With hindsight, do you think you could have avoided your burnout? Was it due to long hours? The type of work? Something else?
I think my biggest since issue was - and probably continues to be - very poor work/life balance (no hobbies, basically no social life outside of work, etc). Obviously it's hard to disentangle cause and effect, but I suspect a prerequisite for getting burnout is having a mania or hyper-fixation on work.
Of course I'd expect someone already burning out to deceive themselves and game their own metrics (like reading and answering emails at night and not counting the time spent).