I can imagine people having fun getting lost in the flow of playing a competitive sport. I've also heard some people experience a post-workout high. But does anyone actually feel pleasure in the moment while lifting weights, jogging, cycling, etc?
If so... what does it feel like? Is there anything the rest of us can do to cultivate such a mindset?
I do. I do it every day, at a public gym/pool. It was originally a way to maintain or regain "ability" (don't call it "fitness", I'm still old and fat). After a while, you start feeling better, and some time after that, start noticing things are getting worse if you don't do it.
For me, doing something fun, out of the house with others, helps a lot. Spin class, circuit training, water aerobics, having others around doing the same thing is motivating. I worked with a trainer for a while, they helped come up with things I like, for example, one of my favorites is tossing a medicine ball. Don't ask me why, but I like that.