Studies have shown that extrinsic motivation can negatively affect intrinsic motivation. In simple language, when people perform tasks for the sake of deriving external rather than internal rewards, their internal motivation and enjoyment is diminished. More specifically, a study examined the enjoyment derived from participants, ranging from preschoolers to college students, who engaged in activities like word games or construction puzzles before and after the addition of extrinsic motivations in the form of dollar bills or candy (Deci, Koestner & Ryan, 1999). The study showed that indeed the addition of external rewards decreased the initial levels of free-choice intrinsic motivation that the participants originally derived from the games (Deci, Koestner & Ryan, 1999)
People may love an activity or a hobby they do, but according to research, when a person gets paid to do that same activity, their enjoyment of it decreases. For example, a teenage rock band may enjoy playing gigs together more than when they eventually make it big and get paid to play at sold out stadiums.
Athletes in professional sports, such as those in the NFL, get paid astonishing amounts to play for professional teams. This is a huge amount of extrinsic motivation for them. These athletes may not enjoy the sport as much in the pros as they did when they played as a child.