The interest of this work was to show the importance of adolescent development in the success of the study.One of the important psychological processes of early adolescence is the second individuation, which involves the creation of their own autonomy, and the formation of young independent personality that is separate from the one he had taken from his parents as a child. Psychological separation adolescents reject characteristics and personality of parents, and attempt to create their own, autonomic. In that sense, the success of adolescent development determined by their ability to cope with the experience of separation.The research was conducted at the University Juraj Dobrila in Pula, at N = 313 students of four generations, from those who enrolled in study program of the academic year 2005/6 to those who enrolled in study program 2008/9 year.In this research we used: Questionary self-concept and (2) Questionary of separation-individuation and (3) Questionary of lifestyle defense mechanisms.The aim was to examine the difference between the groups of students of varying success in (a) the method of mastering with the experience of separation, (b) the use of defense mechanisms, and (c) the level of development of their self-concept. The success of the study defines the three groups (a) who had not completed study program, (b) who are in regular time limit (including apsolvent time limit) completed the study, and (c) who has completed their studies after two or more years.The resulting difference among students in (a) the method of separation of mastering experience shows that students who have prolonged the study program showed greater symbiotic needs.The results obtained of questioning differences among students in (b) the use of defense mechanisms shows that successful students use the mechanisms of regression and repression, while students who have achieved success using weaker mechanisms of intellectualization and projection, respectively students who have used the mechanisms of defense in the service of repression and denial of feelings of anxiety , achieved worse results.With the examination of (c) the development of self concept results show that successful students have a lower sense of incompetence.With this research we confirmed the importance of a successful early adolescent development.Young people who are during the second individuation-separation managed to acquire their own psychological autonomy and self-managed to function and deal with feelings of anxiety arising because of psychological separation, as expected, showed greater academic success.