People grow and live in cultures that deeply influence their values, aspirations and behaviors. However, individuals in their turn play an active role in building their own goals, growth trajectories and social roles, at the same time influencing culture trends. This process, defined psychological selection, is related to the individual pursuit of well-being People preferentially select and cultivate in their lives activities, interests, and relationships associated with optimal experience, a state of deep engagement, concentration, and enjoyment. Several cross-cultural studies confirmed the positive and rewarding features of optimal experience. Based on these evidences, this book offers a new perspective in the study of human behavior. Highlighting the interplay between individual and cultural growth trajectories, it conveys a core message: educating people to enjoy engagement and involvement in activities that can be relevant and meaningful for social welfare is a premise to foster the harmonious development of human communities, and the peaceful cohabitation of cultures.