Good catch! Here is their definition (will update the main post later). Bolding mine:

Vallerand and his colleagues [...] have recently proposed a Dualistic Model of Passion in which passion is defined as a strong inclina-tion or desire toward a self-defining activity that one likes (or even loves), finds important (high valuation), and in which one invests time and energy.

The Dualistic Model of Passion further proposes that there exist two types of passion. The first type of passion is harmonious passion. A harmonious passion produces a strong desire to engage in the activity which remains under the person’s control. This type of passion results from an autonomous internalisation of the activity into the person’s identity (Deci & Ryan, 2000; Vallerand et al., 2003). An autonomous internalisation occurs when individuals have freely accepted the activity as important for them without any contingencies attached to it (Sheldon, 2002; Vallerand, 1997). In such a case, the activity occupies a significant but not overpowering space in the person’s identity and is in harmony with other aspects of the person’s life. An example of such a type of passion would be that with harmonious passion the person strongly loves and values basketball. However, this person also keeps control over the activity and can freely decide when to engage or not in basketball and when to stop engagement. Basketball would then be engaged in because of the pleasure that is drawn from the activity and not from other extrinsic sources (e.g. being popular because of basketball) and leads to a task-focus involvement that is conducive to positive outcomes (e.g. positive affect, flow, concentration).

The second type of passion identified by Vallerand and colleagues (2003) is obsessive passion. This type of passion entails the same strong desire to engage in the activity, as in harmonious passion. However, this desire of engagement is not under the person’s control. Rather, it is as if the activity controlled the person. Obsessive passion results from a controlled internalisation of the activity into one’s identity (Vallerand et al., 2003). Such an internalisation originates from intra and/or interpersonal pressure because certain contingencies are attached to the activity such as feelings of social acceptance, self-esteem, or performance. Thus, although individuals like the activity, they cannot help but engage in it due to a lack of control over these internal contingencies that come to control the person. It is proposed that individuals with an obsessive passion come to develop ego-invested structures (Hodgins & Knee, 2002) and eventually display rigid and conflicted forms of task engagement that preclude the experience of volition in activity engagement. An example of such a type of passion could be a person who strongly loves and values basketball, but because this activity fulfills a strong need for approval or performance which boosts momentarily one’s self- esteem, this person cannot help but engage in basketball, including at times when the activity should not be engaged in or should be stopped. This type of passion should not be confused with the concept of addiction for an activity. An addiction for a daily activity such as sports, gardening, or playing of a musical instrument usually constitutes a very rare pathology. In addition, addictions are often used to describe substance abuse, such as smoking, alcohol drinking, or drug abuse, which can hardly be conceptualised as an activity (gambling might be an exception). Finally, an important distinction between obsessive passion and addiction is that the addict person does not perceive his/her addictive activity as enjoyable anymore, while loving and valuing the activity are core criteria of obsessive passion. Addic- tive gamblers for instance do not like gambling anymore; they want to stop gambling and often seek therapies by themselves or self-exclude themselves from casinos.