Seeking Challenges, Individual Adaptability and Career Growth in the Relationship between Workload and Contextual Performance: A Two-Wave Study

Based on the theoretical approach of the psychology of sustainability and sustainable development and on the theoretical Job Demands-Resources model, this contribution aims to explore the mediating effect of seeking challenges on the relationship between workload and contextual performance and the moderating effects of individual adaptability and organizational career growth in this process. The study involved a convenience sample from different occupational sectors. Data from 178 employees were collected with a self-report questionnaire administered at times T1 and T2 (six months later) and then analyzed through conditional process analysis. Challenging job demands (T1) fully mediated the relationship between workload (T1) and contextual performance (T2); furthermore, individual adaptability (T1) moderated the relationship between workload (T1) and challenging job demands (T1), and organizational career growth (T2) moderated the relationship between challenging job demands (T1) and contextual performance (T2). The results imply that seeking challenges can represent an effective approach to promote sustainable development through improvement of performance at work, maintaining its sustainability over time. The present study is innovative because in the new framework of the psychology of sustainability and sustainable development is able to link workload, seeking challenges, career growth and performance in a two-wave study that not only has theoretical implications for organizations but also operative and practical spillovers.


Introduction
The labor market in recent decades is changing very quickly. We live in an uncertain social and economic environment in which many changes have rapidly modified the working domain. Both work and companies suffer the consequences of these changes. The global crisis of recent years has forced companies to modify their actions to cope with external and internal changes, to be more competitive, to develop innovation and to produce new technologies. Employees are asked to deal with new job demands, some of which are positive, stimulating and exciting because they represent new challenges and new ideas to put into practice, while others are adverse and undesirable (e.g., a heavy workload that negatively impacts on performance). Workers are currently called on to be more proactive, to take the initiative on new ways to accomplish a task, sometimes independently from the type and level of autonomy of the job. Whatever job people are involved in, they can make an important difference and have an essential impact on the organizational results. Employees in their environment may craft and recreate new ways to develop their tasks and to achieve their goals, developing and activating job crafting behaviors. Often unconsciously they are very good crafters, that is, they modify different job aspects to adapt them to their needs, skills and preferences, coping with the challenges and needs deriving from the job [1,2]. Job crafting behaviors, such as seeking challenges, are used to explain what and how specific work conditions affect employee behaviors, but they are used also to describe how employee behaviors can impact and craft the working conditions. Why is seeking challenges crucial nowadays? A possible answer is that attention to organizational well-being is becoming essential in companies because the job demands and resources have a role in predicting employees' well-being, job satisfaction and performance, thus aiding productivity and making companies healthy and sustainable. Promoting health in the workplace also implies improving the performance and well-being of people at work; and in a healthy organization, culture, climate and good practices are able to generate a psychological environment that promotes workers' health, safety and organizational effectiveness [3,4].
The psychology of sustainability, and sustainable development, in fact, represent a new challenging research area which is related to promotion of well-being at work and to psychological well-being of people at work [4][5][6]. Sustainability and sustainable development are related to a psychological perspective, in function of three levels of study: individual, group and organization. Both the psychology of sustainability and the sustainable development are centered to the well-being of the individual and to the well-being of the environment, but they also aimed to explore the person in the environment, considering different kinds of environments: natural, personal, social, organizational, community, global and cross-cultural environments [5,6]. At an individual level, the focus is on the personal resources for sustainability [4][5][6]. At an organizational level, a healthy organization, considered as a system opened to the challenges, is aimed at creating a climate and a culture characterized by sustained creativity and innovation, and a happy place for employees and employers [6,7].
Thus, bearing in mind the importance that job crafting behaviors can have in sustainable workplaces, a two-wave study was designed where we focused on the role that seeking challenges might play in the relationship between workload and contextual performance. Moreover, we also wanted to investigate in which specific conditions this process might occur by exploring the moderator role played by individual adaptability and organizational career growth. Figure 1 depicts the tested model. with new job demands, some of which are positive, stimulating and exciting because they represent new challenges and new ideas to put into practice, while others are adverse and undesirable (e.g. a heavy workload that negatively impacts on performance). Workers are currently called on to be more proactive, to take the initiative on new ways to accomplish a task, sometimes independently from the type and level of autonomy of the job. Whatever job people are involved in, they can make an important difference and have an essential impact on the organizational results. Employees in their environment may craft and recreate new ways to develop their tasks and to achieve their goals, developing and activating job crafting behaviors. Often unconsciously they are very good crafters, that is, they modify different job aspects to adapt them to their needs, skills and preferences, coping with the challenges and needs deriving from the job [1,2]. Job crafting behaviors, such as seeking challenges, are used to explain what and how specific work conditions affect employee behaviors, but they are used also to describe how employee behaviors can impact and craft the working conditions. Why is seeking challenges crucial nowadays? A possible answer is that attention to organizational well-being is becoming essential in companies because the job demands and resources have a role in predicting employees' well-being, job satisfaction and performance, thus aiding productivity and making companies healthy and sustainable. Promoting health in the workplace also implies improving the performance and well-being of people at work; and in a healthy organization, culture, climate and good practices are able to generate a psychological environment that promotes workers' health, safety and organizational effectiveness [3,4]. The psychology of sustainability, and sustainable development, in fact, represent a new challenging research area which is related to promotion of well-being at work and to psychological well-being of people at work [4][5][6]. Sustainability and sustainable development are related to a psychological perspective, in function of three levels of study: individual, group and organization. Both the psychology of sustainability and the sustainable development are centered to the well-being of the individual and to the well-being of the environment, but they also aimed to explore the person in the environment, considering different kinds of environments: natural, personal, social, organizational, community, global and cross-cultural environments [5,6]. At an individual level, the focus is on the personal resources for sustainability [4][5][6]. At an organizational level, a healthy organization, considered as a system opened to the challenges, is aimed at creating a climate and a culture characterized by sustained creativity and innovation, and a happy place for employees and employers [6,7].
Thus, bearing in mind the importance that job crafting behaviors can have in sustainable workplaces, a two-wave study was designed where we focused on the role that seeking challenges might play in the relationship between workload and contextual performance. Moreover, we also wanted to investigate in which specific conditions this process might occur by exploring the moderator role played by individual adaptability and organizational career growth. Figure 1 depicts the tested model.

The Mediating Role of Seeking Challenges in the Relationship between Workload and Contextual Performance
Seeking challenges is a form of proactive behavior that can be sustainable over time and is able to guarantee good balance between job demands and job resources. Seeking challenges is part of the concept of job crafting involved in the theoretical framework of the Job Demands-Resources (JD-R) model [8]. In this model, the job resources and job demands activate two different processes: a health-impairment process and a motivational process [9]. The JD-R theory explores how and which job characteristics can lead to negative or positive individual and organizational outcomes, considering two broad classes of working conditions (job demands and job resources). Job demands are job characteristics potentially adverse if not aligned with the abilities of individuals to adapt themselves to changes. Job resources are job aspects, which can give an essential support to employees [9] and are described as the physical, psychological, social or organizational job characteristics, which realize different purposes. Job resources are crucial in accomplishing work goals and are necessary to harmonize the balance with the job demands. While many issues of this model are clear, one of the unresolved issues is related to the different types of job demands. Job demands are aspects of work that require effort, so they have a role in health-impairment processes and thus can impair job performance. According to Cavanaugh et al. [10], it is crucial to consider 'challenge' and 'hindrance' demands in order to study the theoretical and practical implications for organizations. This distinction is elicited also by the JD-R model and thus the job crafting literature. Challenge demands have a positive side and give an opportunity for personal growth and reward (fair workload, starting a new project, learning new skills) [8]. To the extent that they are not too excessive, these challenge demands can be positively related to job performance. On the other hand, hindrance demands are stressful requirements (long-term exposure to high job insecurity, role ambiguity, role conflict, heavy workload, role overload, time pressure, cognitive and emotive demands) [8] that decrease the chance to improve personal growth and are often negatively related to job performance. Challenge demands might be experienced as hindrance demands (and vice versa), depending on the context: They can have a psychological and physical cost but potentially can promote personal growth and goal achievement; they can be a heavy workload, time pressure and responsibility [11]. Workload may be a good or bad stressor, depending on the context and the variables related to it. This implies a complexity in studying the relationship between job demands and organizational outcomes such as performance at work.
According to the JD-R model, scholars identified some job crafting dimensions related to resources and demands [1,12,13]. Petrou et al. [14] classified three distinct job crafting behaviors: seeking resources, seeking challenges and reducing hindrance demands. Seeking resources can be valued as a form of coping with job demands; it concerns feedback, advice seeking from colleagues or supervisors, maximizing job autonomy, etc. Reducing demands includes behaviors targeted at decreasing the emotionally, mentally and/or physically demanding elements of one's work. Seeking challenges concerns all those behaviors (starting new projects, asking for or accepting more responsibility, etc.) that lead individuals to develop knowledge and skills that can help them to manage difficult goals and increase their job satisfaction and motivation, thus improving their performance at work [12]. Thus, as workload and seeking challenges might be intercorrelated, we hypothesized that seeking challenges could be a way in which individuals can adapt to cope with the negative consequences of workload, and through this process achieve positive outcomes such as contextual performance. In this study we focused on the relationship between workload, seeking challenges (as a positive job demand) and contextual performance. Contextual performance is a form of extra-role behavior to measure performance at work. In recent decades there has been increasing consideration of flexible and positive work behaviors that, indirectly, can add value to the goals of the organization. Different labels have been used for this type of behavior: organizational citizenship behavior, extra-role behavior and contextual performance [15]. Contextual performance behaviors help the organizational, social and psychological environment in which the technical core must function. Examples of contextual actions are volunteering, persisting, helping, cooperating and following rules. While the task activities are specific for each job, contextual activities can be common to many or all jobs. Contextual performance is voluntary, either altruistically or intrinsically motivated [16], and by providing extra support it helps organizations to maintain a sustainable, healthy social work climate [17]. In summary, contextual performance refers to all those behaviors and activities not necessarily related to the work task but that can contribute to the social and psychological work climate [18]. Moreover, contextual performance can enhance the organizational effectiveness since it 'includes volunteering to carry out task activities that are not formally part of the job and helping and cooperating with others in the organization to get tasks accomplished' [19] (p. 100). Workers are generally suggested to show extra-role behaviors when they are highly motivated [20,21].
Thus, hypothesizing the mediating role that seeking challenges might play in the relationship between workload and contextual performance, we put forward the following hypothesis: H1. Seeking challenges at time T1 will mediate the relationship between workload at T1 and contextual performance at T2.

The Moderating Role of Individual Adaptability in the Relationship between Workload and Seeking Challenges
Workload concerns the feeling that one has too many things to do in too little time. It has often been related to burnout [22] or workplace bullying [23,24], and it might be one of the antecedent variables of workaholism [25]. Meta-analyses [26,27] evidenced that workload and time pressure were strongly related to emotional exhaustion and disengagement. Workload is also often studied in relation to exhaustion and disengagement because of the increased effort that is needed when employees have the feeling that they need to do more at work. Disengagement, thus, is often related to interpersonal conflicts [28,29]. Intense negative emotions derived from being in conflict with colleagues [30] can explain the relationship between conflict at work and the tendency of employees to disengage from their work. So, in a positive framework, we hypothesized that being able to control one's emotions and being adaptable and flexible can help to manage interpersonal relations at work and regulate the relation between workload and proactive behaviors. Companies require employees to be more flexible, self-initiating and self-regulating [31]. An example of self-regulating work behavior is the seeking of challenges and new projects at work [32]. Research has shown that seeking challenges may stimulate personal growth and adaptability, and vice versa [12,33]. Ployhart and Bliese [34] defined adaptability as ''an individual's ability, skill, disposition, willingness, and/or motivation, to change or fit different task, social, and environmental features" [34] (p. 13). Adaptability is a positive motivational orientation toward changing oneself [35]. Employee adaptability is also a good predictor of job crafting behaviors [35] and can positively affect the relationship between workload and the seeking of challenges. A flexible workforce allows the companies to meet changing performance requirements, adapt and reply to innovations [36]. Thus, organizations value employees who have the ability to adjust to changing expectations and capitalize on opportunities that enhance their skills [14,37,38]. For this reason, we hypothesize that: H2. Individual adaptability at T1 will moderate the direct effect of workload at T1 to seeking challenges at T1 in the way that the relationship between workload and seeking challenges will be stronger at a higher level of adaptability than at a lower level.

The Moderating Role of Organizational Career Growth in the Relationship between Seeking Challenges and Contextual Performance
Organizational career growth (OCG) focuses on career management beyond the choices made by individuals, with the aim of recognizing that the role of the organization in managing careers is crucial as well [39]; OCG refers to one's employment within a single organization and has been closely linked to several important work outcomes, such as job satisfaction, performance (e.g. [39]) and employee voice [40]. According to several authors [41,42], some organizational processes influence the extent to which employees perceive a psychological contract obligation with their employers. Specifically, when merit determines the career and growth prospects of employees they are more likely to perceive that their expectations have been met, because it is logical to assume that providing reasonable career growth and opportunities to advance may be perceived by employees as a reasonable obligation on the part of the organization. Human resources practices have a significant impact on the extra-role behavior, such as contextual performance. However, to the best of our knowledge there is a lack of literature on the moderating role of OCG in the relation between seeking challenges and contextual performance. In this study we aim to fill a gap, looking at OCG as a variable that moderates the impact of seeking challenges on contextual performance. Our hypothesis is: H3. Organizational career growth at T2 will moderate the direct effect of seeking challenges at T1 to contextual performance at T2 in the way that the relationship between seeking challenges and contextual performance will be stronger at a higher level of OCG than at a lower level.

Procedure
A first self-report questionnaire was administered to a sample of 188 employees at time T1. This questionnaire included some of the variables in the study (workload, adaptability, seeking challenges) and also the socio-demographic variables. Participants were contacted through graduating students who helped to administer the questionnaire. Then, six months later at time T2 a second questionnaire assessing OCG and contextual performance was administered to the same sample. A total of 10 participants failed to complete the second questionnaire.

Ethical Aspects
The procedure was in accordance with the standards of the national law of data treatment followed by the University of Turin, University of Salento and University of Campania (Italy). Since there was no medical treatment or other procedures that could cause psychological or social discomfort to the participants, who were all adult healthy subjects anonymously involved, additional ethical approval was not required according to the Institution. The research was conducted in line with the Helsinki Declaration [43] and with the data protection regulation of Italy (Legislative Decree No. 196/2003). Participation in the research was voluntary and not rewarded; data collection and analysis were anonymous. A cover letter attached to the questionnaire provided information about the study aims, guarantees about anonymity, voluntary participation and data treatment, plus instructions for filling out the questionnaire. By agreeing to fill out the questionnaire, all study participants provided their informed consent.

Measures
Workload. Six items adapted from Theorell et al. [44] were used to measure workload. Item example: 'I have to work very fast'.
Individual adaptability. Five items from the scale proposed by Ployhart and Bliese [34] were used to measure individual adaptability. Items are: 'I enjoy learning new approaches for conducting work'; 'I am able to make effective decisions without all relevant information'; 'I usually overreact to stressful news'; 'I believe it is important to be flexible in dealing with others'; 'I enjoy learning form cultures other than my own'.
Seeking challenges. Three items from the scale developed by Petrou et al. [14] were used to measure the seeking of challenges in job crafting behaviors. Item example: 'I ask for more odd jobs'.
Organizational career growth. The scale developed by Weng and Hu [45] and adapted in Italy by Spagnoli and Weng [46] was used to measure the four dimensions of OCG: career goal progress, professional ability development, promotion speed and remuneration growth. Career goal progress was measured by four questions: Item example-"My present job moves me closer to my career goals". Professional ability development was measured by four questions: Item example-"My present job encourages me to continuously gain new and job-related skills". Promotion speed was measured by four questions: Item example-"My promotion speed in the present organization is fast". Finally, remuneration growth was measured by three questions: Item example-"My salary is growing quickly in my present organization".
Contextual performance. Contextual performance was measured by eight items adapted from Koopmans et al. [15]. Item example: 'I started new tasks myself, when my old ones were finished'.
All the variables were measured using a Likert scale ranging from 1 (completely disagree) to 5 (completely agree). For each variable in this study, Cronbach's alpha coefficients are reported (see Table 1).

Data Analysis
Cronbach's alpha coefficient and zero-order correlations were used to assess the internal consistencies of the scales and to examine the associations between variables. The hypotheses concerning direct, mediated and moderated effects were tested through bootstrapping-a non-parametric resampling procedure that does not assume normality and involves the extraction of several thousand subsamples (5000, in our case) from a dataset. Through bootstrapping, the distribution of effects is approximated empirically and used for calculating confidence intervals [47]. Specifically, the model examined in the current study corresponds to conceptual model number 21 of Hayes' templates [48]. Table 1 shows the zero-order correlations among study variables and their reliability measured by Cronbach's alpha coefficient. Contextual performance at T2 was positively and significantly related to all the other variables in the model, except for the control variables. Seeking challenges at T1 was positively and significantly correlated to OCG at T2 and workload at T1, where it was negatively and significantly correlated to the control variables. No correlation was found between seeking challenges at T1 and individual adaptability at T1. Individual adaptability at T1 was positively and significantly correlated to all the variables, except for seeking challenges at T1 and OCG at T2. OCG at T2 was positively and significantly related to contextual performance at T2 and seeking challenges at T1, whereas it was not related to workload at T1 or individual adaptability at T1. Moreover, OCG at T2 was negatively and significantly related to all the control variables. Cronbach's alpha coefficient ranged from 0.66 to 0.95 (see Table 1). Despite these values, individual adaptability is less than 0.70; this variable can be included in the study since Cronbach's alpha coefficient can be smaller if the number of items in the scale is fewer than ten [49]. Because individual adaptability is composed of five items, this measure has been considered here.

Results
Successively, two models were tested: Model 1, which represents a simple mediation model where job crafting at T1 mediates the relationship between workload at T1 and contextual performance at T2; and Model 2, which represents Model 1 but adding the two interactions between workload at T1 and adaptability at T1 in relation to seeking challenges at T1, and between job crafting at T1 and OCG at T2 in relation to contextual performance at T2. Gender, age and tenure were inserted in the models as control variables. Input variables were centered in order to compute the interaction terms. Table 2 reports the results for the conditional process analysis conducted on the two models. The results showed the existence of a total mediation effect of seeking challenges at T1 in the relation between workload at T1 and contextual performance at T2. In fact, introduction of the mediator made the significant direct effect of workload at T1 on contextual performance at T2 not significant. In particular, the mediating effect explained 20% of the variance of the direct effect (Model 1: R 2 = 20). Thus, hypothesis H1 was supported.
Moreover, the interactions terms were statistically significant. In particular, although individual adaptability at T1 was not directly related to seeking challenges, when computed in the interaction the effect of the interaction was highly positively significant, indicating the moderating role of individual adaptability. The plot of the interaction can be observed in Figure 2. Simple slope analysis revealed that the effect of workload is significant only at a higher level of individual adaptability (B = 0.36; p < 0.001); at a lower level of individual adaptability the relationship between workload and seeking challenges is not significant (B = −0.07; p = 0.55). Thus, hypothesis H2 was supported.
Moreover, the interactions terms were statistically significant. In particular, although individual adaptability at T1 was not directly related to seeking challenges, when computed in the interaction the effect of the interaction was highly positively significant, indicating the moderating role of individual adaptability. The plot of the interaction can be observed in Figure 2. Simple slope analysis revealed that the effect of workload is significant only at a higher level of individual adaptability (B = .36; p < .001); at a lower level of individual adaptability the relationship between workload and seeking challenges is not significant (B = −.07; p = .55). Thus, hypothesis H2 was supported.
Additionally, as hypothesized, OCG moderated the relationship between seeking challenges and contextual performance, such that a lower level of both seeking challenges and career growth would lead to the lowest level of contextual performance, whereas a higher level of both seeking challenges and OCG would lead to the highest level of contextual performance. However, the impact of OCG seems wider when seeking challenges is low rather than when seeking challenges is high, indicating that when seeking challenges is high the effect of OCG is small. In fact, a simple slope analysis (Figure 3) reported that the stronger effect of seeking challenges happened when the moderator OCG was lower (B = .34; p < .001) than when it was higher (B = .13; p < .05). Thus, hypothesis H3 was only partially supported.  Additionally, as hypothesized, OCG moderated the relationship between seeking challenges and contextual performance, such that a lower level of both seeking challenges and career growth would lead to the lowest level of contextual performance, whereas a higher level of both seeking challenges and OCG would lead to the highest level of contextual performance. However, the impact of OCG seems wider when seeking challenges is low rather than when seeking challenges is high, indicating that when seeking challenges is high the effect of OCG is small. In fact, a simple slope analysis (Figure 3) reported that the stronger effect of seeking challenges happened when the moderator OCG was lower (B = 0.34; p < 0.001) than when it was higher (B = 0.13; p < 0.05). Thus, hypothesis H3 was only partially supported.

Discussion
The aim of this study was to examine the mediating effect of seeking challenges in the relationship between workload and contextual performance; the study also aimed to verify the moderating effects of individual adaptability and OCG in this model. Our results pointed out that it is valuable to explore the role of seeking challenges, not only as a mediator between several variables but also to identify its possible moderating variables. Firstly, we found that seeking challenges fully

Discussion
The aim of this study was to examine the mediating effect of seeking challenges in the relationship between workload and contextual performance; the study also aimed to verify the moderating effects of individual adaptability and OCG in this model. Our results pointed out that it is valuable to explore the role of seeking challenges, not only as a mediator between several variables but also to identify its possible moderating variables. Firstly, we found that seeking challenges fully mediated the relation between workload and contextual performance. Several forms of job crafting can be used to cope with workers' workload. These types of job crafting, such as seeking resources or seeking challenges, can be made by organizational changes; in particular, seeking challenges, as a form of proactive job demand, offers opportunities to improve the impact of workload on contextual performance. Job challenges allow employees to stay involved in their tasks and to grow and thrive [50]. Challenges activate employees' coping resources and result in 'outstanding performance' [51] (p. 5). Moreover, according to Petrou et al. [14], by the accumulation of new abilities, this active approach encourages people to achieve high performance and efficiency [52]. Seeking challenges, moreover, may help employees to improve their strategies for adjusting during change [53] and, thus, enhance performance at work. In summary, seeking challenges provides workers with the skills needed for goal achievement, and it can be considered a resilient strategy against exhaustion [14]. Secondly, we found an important moderating role played by individual adaptability in the relation between workload and seeking challenges. Under some conditions, namely when people are adaptable, workload can be related to challenging job demands. Adaptability is a crucial component of career development, especially in the current workplace where changes and modifications are usual and happen regularly. Adaptability leads to familiarity with change-related activities and can increase the ease with which change is performed in similar situations in the future [54]. Being adaptable means being 'sustainable' for oneself and for the company-the actual organization or for future organizations in one's career. Adaptable people have a high tolerance for uncertainty and are able to cope with new and challenging situations; they can also cope when they live with career insecurity (e.g., because of the type of contract) or unemployment [55].
In a boundaryless career perspective, well-being at work is a key sustainable development goal; it also represents a requirement for good health and is part of organizational life and human resources strategic management [56]. The third result of our study concerns the moderating role of OCG in the relationship between seeking challenges and contextual performance. Surprisingly results indicated that when seeking challenges is high the effect of OCG is negligible, whereas when OCG is low and seeking challenges is low as well their interaction has a higher effect on contextual performance. This result is not in line with the literature, because a career growth policy should generate strong feelings of a psychological contract among employees of the organization, particularly when the career growth policy is a valued initiative for employees [57] who anticipate progress and growth in their careers [58]. Furthermore, according to Okurame [59], high and positive levels of performance evaluations are traditional requirements for hierarchical advancement in a career. Although these findings are counterintuitive, several reasons could explain them. First, the methodological aspect linked to the time at which seeking challenges and OCG were measured could have impacted the perception of the participants, particularly in relation to the moderating and outcome variables. In fact, seeking challenges was measured at T1 whereas OCG (as well as contextual performance) was measured at T2. A proper three-wave study should be adopted in future studies in order to better clarify these relationships. A recent study by Spagnoli and Lo Presti [60] shows new, interesting evidence regarding a possible negative role that OCG could play in the work-family dynamic. Specifically, Spagnoli and Lo Presti reported a significant positive relationship between OCG and work-family conflict, probably due to the workplace demands associated with the opportunity to advance one's career (e.g., long working hours). This result sheds some light on the need for a more in-depth study of the role that OCG might play in improving the quality of working life for different categories of employees. Thus, it can be possible that other individual moderators could have a role in the relationship between job challenges and OCG in relation to contextual performance. These findings can be read in the perspective of the psychology of sustainability and sustainable development which are focused on the well-being of the person and of the environment, and also on the well-being of the person in the environment, considering different kinds of environments: natural, personal, social, organizational, community, global and cross-cultural environments [5]. This perspective emphasizes the sustainable development of every person, by facilitating the flourishing of own skills and an improvement of own quality of life, which, thus, becomes not only a personal growth but also a benefit of the community of belonging and progress. In summary, also in the perspective of the psychology of sustainability and sustainable development [4][5][6] more research is needed to unveil the complexity of the relationships between these variables, and other dimensions, such as life satisfaction and job insecurity need to be explored [2,61].

Limitations and Theoretical and Practical Implications
A first limitation of this study concerns the convenience sample involved. Since this is a heterogeneous sample of workers, we could not control for the specific organizational contexts, which could have a role, for example, in determining the degree of autonomy of the worker in implementing job crafting and in the perception of career development possibilities. Future research should replicate the model in different companies; moreover, it could be useful, through multi-group analysis, to test differences among workers and suggest focused organizational interventions. Secondly, we used a self-reported instrument, which may not be free from common method variance bias; this limitation should be controlled in future studies. Third, the time lag we opted for our study was six months. This choice could be insufficient to formulate definitive conclusions on the investigated process. In fact, despite this is a better and more robust methodological solution than cross-sectional studies for detecting mediation effects, a more proper longer three-waves study could have been adopted. Forth, as far as the measure of individual adaptability is concerned, we used just a few items of a very long original scale. A proper Italian adaptation and validation of the original scale, or better, its shorter version should be addressed in future studies. Finally, future studies should explore the seeking of challenges through behaviors oriented to proactively adapt the job to personal or family needs, in order to focus also on the specific dynamic that links the job and the individual. Results of this study highlight how companies may gain by having human resources management aimed at promoting job crafting behaviors-precisely all those particular forms of seeking challenges in one's own job. Moreover, human resources should consider applying job crafting practices to improve performance and productivity. Therefore, offering focused training to make employees aware of the potential of job crafting and also to avoid the wrong types of self-organization could be a key factor. In particular, it could be useful to develop the consciousness of the challenging side of demands, since it is associated with engagement and development to accomplish job tasks [62].