You Have to Feel It

The only thing you have to do is pay taxes and die. It does help to feel good about the project and the work, but it is not a requirement for a fulfilling life.

Looking back at most times I have felt horrible in the depth of adversity, resistance or burnout I realize those were the times of greatest potential for achievement, learning and growth. Those are the memorable chapters, the things that define my character. The times when I continued to grind, continued to push through and didn't give up because of feelings were the times when I actually accomplished something: raised a kid, bought a house, switched continents.

I think you are using different concepts of "feel good". "Feeling good" doesn't exclude adversity or resistance. But it should be resistance where you have reasonable grip on it, with some traction, and it's aiming towards something that you value. Neither trivial, nor so hard that you have no way of getting traction with it, being stuck on zero progress.

Happiness is basically equivalent to feeling steady (even if slow) progress in response to one's own effort towards valued goals.

I have often felt bad (or "didn't feel it" to quote this article) and it still turned out OK because I showed up and stuck with it.