This is my conclusion too. Frustratingly, productivity seems to be mostly downstream of good self-care: exercise, good sleep, avoiding caffeine, and good diet

This is my conclusion too. Frustratingly, productivity seems to be mostly downstream of good self-care: exercise, good sleep, avoiding caffeine, and good diet in my personal descending order of importance. It sucks that they're interrelated, and one of those, good sleep, can be a biological dice roll, and that the other three are things I'm tempted to burn on the altar of extra productivity in the short-term when it just decreases it in the long-term. :p