I'd make the crazy (/s) argument that the mindset, not the eat well/exercise/sleep is what matters. I tried endlessly during my PhD to eat healthy, sleep well,

I'd make the crazy (/s) argument that the mindset, not the eat well/exercise/sleep is what matters. I tried endlessly during my PhD to eat healthy, sleep well, and such but this only worked when I truly realized 'ok, my normal routine is killing me', like OP did. It's scary because that's how you know yourself to be / work but once you have no alternatives it is easier to risk a productivity deficit (.:. it's also easier when you're more confident about your achievements so far and don't think you have to prove as much of yourself to others). Luckily for me the marginal productivity deficit is totally compensated by living a burnout-free life. (I hope. Ask me again in 5-10 years)