I think so, yeah. Aside from not listening to the obvious warning signs (insomnia, anxiety, depression, increased frequency of physical illness, etc.), there were definitely other red flags.

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.

Interesting, thanks! It seems that, in your case at least, making sure that you don't work more than, say, 45h a week could have helped. Not saying it's easy to do or that it solves everything, but it feels easier to improve things you can measure.

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).

Don’t have stress. It’s that simple. No idea how you’d fix it though. (And IMO long periods of tedious work counts as stress too)