It thus appears that harmonious 
(but not obsessive passion) contributes to psychological well-being in both younger and older populations using a number of measures, providing some support for the major hypothesis regarding the promotion of psychological well-being and the prevention of ill-being
Third, Lyubomirsky and colleagues never completely state the nature of the processes at play in their model. They repeatedly mention that self-concordant goals that are attained preferably in new activities will lead to positive effects on one’s well-being. But not much else is mentioned regarding what it is that leads to the positive effects on well-being. What I suggest (and elaborate on in a later section) is that in line with Fredrickson (e.g., 2001), positive emotions and associated processes represent the important mechanisms that facilitate the positive effects of harmonious passion on well-being. This is because positive emotions lead one to expand the self and to broaden one’s repertoire of skills (Fredrickson 2001). Positive emotions could explain why Lyubomirsky and their colleagues find that new activities and those where there is goal attainment to have positive effects on one’s psychological well-being as such emotions are likely to be experienced under these conditions.
Thus, the thesis advanced here is the following. Because harmonious passion leads the person to experience positive emotions during activity engagement that, in turn, facilitate increases in psychological well-being, and because harmonious passion leads to activity engagement and thus to the experience of positive emotions on a regular basis (roughly 8 hours per week), it is posited that harmonious passion leads to increases in psychological well-being that are sustainable. Thus, passion for the activity is important because it is the motivational force that leads the person to engage in the activity on a regular basis. It is proposed that to the extent that one’s passion is harmonious, then this will set in motion two positive functions: promoting psychological well-being and preventing the occurrence of ill being. However, if one’s passion is obsessive, then the positive effects may not be forthcoming on psychological well-being and an increase in ill-being may even take place. I elaborate on the empirical support for the proposed effects and processes in later sections.
Further, the type of effects that will be experienced on a regular basis depends on the type of passion one has for such an activity
Our initial research sought to determine if there was a link between passion for an activity and psychological well-being. It involved senior citizens (Rousseau & Vallerand 2003). We included measures of both psychological well-being such as life satisfaction (Diener et al. 1985), meaning in life (Steger et al. 2006), and vitality (Ryan & Frederick 1997), as well as psychological ill-being ( scales of anxiety and depression from the General Health Questionnaire of Goldberg & Hillier 1979). In line with the above hypotheses, having a harmonious passion for an activity was expected to promote psychological well-being, while being obsessively passionate or non passionate was not. Furthermore, it was also hypothesized that harmonious passion should protect against ill-being because of the positive affective states it facilitates. Research supported these hypotheses. For instance, in this particular study, we found that harmonious passion toward one’s favorite activity (e.g., playing cards, playing a musical instrument) positively predicted positive indices of psychological well-being but negatively predicted indices of ill-being. Conversely, obsessive passion positively predicted anxiety and depression, was negatively related to life satisfaction, and was unrelated to vitality and meaning in life. Thus, the promoting and protective functions of harmonious passion were supported while the less than optimal role of obsessive passion was demonstrated.
Subsequent research with young adults and teenagers has yielded similar findings. Specifically, harmonious passion toward activities such as sports, dramatic arts, work, and specialized areas of education was found to be positively related to life satisfaction and vitality (Houlfort et al 2011, Studies 1 and 2; Vallerand et al. 2008, Study 2), whereas obsessive passion for the same activities was either negatively related (Houlfort et al. 2011; Vallerand et al. 2007, Study 2) or unrelated (Vallerand et al. 2007, Study 1; Vallerand et al. 2008, Study 2) to these indices.