Based on the medical model, psychology has focused its efforts more to the scientific study of the dysfunctional aspects of an individual, rather than its potential. This has generated instability in the field of study of this science that by focusing his attention almost exclusively on human problems, eventually leaving topics such as happiness, to be appropriate by the so called self-help literature, very popular in countries like Brazil . As a result of a doctoral dissertation, this book discusses human happiness in a scientific point of view and based on the theoretical framework of Positive Psychology. We believe that this approach is key to building a consistent body of theory on the subject and able to assist in developing mental health programs with a preventive character. However, for this to happen, we need to develop research to investigate the various aspects involved in human happiness and flourishing. In this sense, the study presented in this book which we conducted with 106 Brazilian university students about the relation between happiness and locus of control is an important contribution.