The theoretical model presented in this paper emerged from several different disciplines. This model proposes that the attainment of happiness is linked to the self, and more particularly to the structure of the self. We support the idea that the perception of a structured self, which takes the form of a permanent, independent and solid entity leads to self-centered psychological functioning, and this seems to be a significant source of both affliction and fluctuating happiness. Contrary to this, a selfless psychological functioning emerges when perception of the self is flexible (i.e., a dynamic network of transitory relations), and this seems to be a source of authentic-durable happiness. In this paper, these two aspects of psychological functioning and their underlying processes will be presented. We will also explore the potential mechanisms that shape them. We will conclude with an examination of possible applications of our theory.