There is a long tradition assuming that personality is set like plaster. In recent years, a controversy arose about the appropriateness of the assumption that personality does not change after the age of 30 and is mainly influenced by genes. In this talk, I will focus on the questions of (a) when, (b) how, and (c) why personality changes in adulthood. Using data of the Big Five personality traits from the SOEP and applying different statistical approaches, me and my colleagues arrive at the following conclusions: (a) personality changes across the whole life span with most changes before the age of 30 and after the age of 70, (b) conscientiousness and agreeableness increase whereas openness decreases with age, (c) major life experiences influence personality development and personality maturation is most likely when developmental tasks are successfully mastered. Taken together, reaching a mature personality takes a long journey and can partly be influenced by ourselves.