I saw a video today of a skiier going down a mountain and you could see that he was most definitely in the flow. He was moving from one slope to another, jumping around and doing flips, and doing it with such ease. It was obviously not easy, and getting to this point probably took years of skiing. All I see is such difficult terrain, it's not easy at all to navigate fresh pow on such a big mountain, but for him it's easy. He's gliding like a hot knife on butter. It's amazing to me, but it's just another fun day for him.
There's a superb confidence that comes when something that others consider difficult becomes play for you. Maybe there is some kind of evolutionary advantage from having fun. Maybe the reason humans can go so deep into complex, difficult, and obscure areas of study because it's fun to some humans.
For me coding is fun. I'll spend a weekend on a project no problem, I love it. But this is not the case for most of the people I've met. Coding is not fun for everyone. And I think that's interesting.