I saw a cartoon that captured this pretty well; a pianist who looks pensive, thinking "I don't enjoy this at all". The caption is something like "how to know you're a professional".

Everybody runs this risk, but "creative" jobs probably more so. Not being able to enjoy what you're doing even if you're successful. It may be because there's always a pressure to improve. But it could also be because the inner motivation that used to drive you has been replaced with external rewards. C. Thi Nguyen calls it "value capture".

I agree with the author's friend in that it's up to each of us to find creativity, it must come from within.