The purpose of the present paper is to present the Dualistic Model of Passion (Vallerand et al., 2003) and show its importance for positive psychology. Passion is defined as a strong inclination toward a self-defining activity that people like (or love), find important, and in which they invest time and energy. Furthermore, two types of passion (harmonious and obsessive) are proposed. Harmonious passion leads people to choose to engage in the activity that they love. Conversely, obsessive passion creates an internal pressure to engage in the beloved activity. Harmonious passion is hypothesized to lead to more adaptive outcomes than obsessive passion. Results of several studies reveal that passion matters with respect to a number of outcomes deemed important for positive psychology such as flow and positive emotions, psychological well-being, physical health, relationships, and performance. Passion can indeed make people's lives worth living to the extent that it is harmonious in nature.