In integrated approaches to personality (McAdams & Pals, 2006; McCrae & Costa, 1999), it is possible to examine relationships between personality traits, beliefs as characteristic adaptations, and subjective well-being. This research aimed to verify if implicit self-theories (belief about stability of human nature) proposed by Dweck (2000) and life-engagement proposed by Scheier et al. (2006) play a mediating role in relationships between personality traits and satisfaction with life. The relationships were examined with respect to infertility problem. A sample of 120 adults (aged 26–48; M = 36.60; SD = 4.82; 50% women) participated in the research. The mediation hypotheses were examined, and furthermore, four groups of couples were compared in terms of measured variables. The groups were: couples with (1) cured and (2) uncured infertility and couples who were not infertile and (3) have and (4) do not have children. Life-engagement mediated the relationship between Conscientiousness and satisfaction with life in the whole sample. The belief about stability of human nature mediated relationships between subjective well-being and Conscientiousness, Agreeableness, Neuroticism, and Extraversion only among couples with an infertility problem.