Much has been achieved with regard to how critical life events influence trajectories in life. Theories on the development of personality and well-being emphasize that people differ in the rate, timing, and direction life events influence certain personality traits and key indicators of well-being such as life satisfaction. However, there has been an urgent call for longitudinal studies exploring processes that underlie individual differences of the appraisal and reaction to critical life events. This dissertation seeks to meet this plea by investigating the influence of specific and non-specific critical life events on personality development and life satisfaction, taking into account one’s subjective perception of these events. Since core beliefs can alter mental representations of life events, the present dissertation explores a possible moderating role of mindset and self-efficacy. Moreover, this dissertation places particular focus on the assessment of life events and implications for the critical age periods of adolescence and emerging adulthood. While the first longitudinal study (N = 1,243) focusses on the influence of two specific life events, school graduation and moving away from the childhood home, on trait changes in the Big Five, the second study (N = 1,477) explores personality development below the domain level in trait intellect, a facet of openness, with regard to predominantly non-specific life events. The third study (N = 1,920) expands the scope of the current thesis by considering the impact of a collective experienced life event, the COVID-19 pandemic, on the development of life satisfaction over four measurement occasions. Across the three studies, I investigate individual differences by considering the moderating role of the core beliefs of mindset or self-efficacy. Although none of the studies suggest that these critical life events have an influence in and of themselves, results reveal significant personality changes (Study 1) and changes in life satisfaction (Study 3) when taking into account subjective perceptions of the critical life events. Further, the results of studies 1 and 2 indicate personality development in traits that are associated with mature functioning. While a moderating role of mindset was found in study 1 regarding the influence of the perception of the life event graduation on levels in extraversion and neuroticism, results indicated no moderating effects of self-efficacy in the studies 2 and 3. However, the present results reveal selection and socialization effects of self- efficacy with respect to the development of intellect (Study 2), and significant effects of self-efficacy on life satisfaction before and during the COVID-19 pandemic (Study 3). All in all, the present findings contribute to a deeper understanding on the processing of life events, but further longitudinal studies are needed to observe individual life trajectories in young adulthood with respect to different event characteristics and implicit beliefs. In the conclusion, limitations of this dissertation, future research ideas, as well as practical implications for adolescents and emerging adults are discussed.
