I have a similar experience. I was a devoted PhD student working long hours taking on a lot of responsibility. It burned me out, hurting my productivity. I have mixed feelings about it; I love the friends I made and the things I learned, but I don’t think I should have had to suffer what I suffered. Simultaneously I’m somewhat glad I experienced it then, because now I work in tech and I’ll _never_ work outside of business hours (I’ll hack on personal projects I consider fun if I feel like it). And I’m more productive than my colleagues that do. There’s something mysterious about the contemporary PhD, not all good and not all bad.