[neuroma]

Respectfully, to say you did something for at least half of your adult days, but that it wasn't rewarding, is perhaps a misuse of the term reward.

I'd suggest that whilst you may have suffered in doing the exercise for whatever reason, there was also a parallel and strong reward process embedding and sustaining that behaviour in you.

[klodolph]

I think that's an overbroad notion of "reward". You have a certain point, but it may be seen as kind of a behaviorist way of looking at things, and the behaviorist approach fails to provide the same insight into mind that other approaches have.