I have very clear advice for PhD: Agree to work 4 hours a day on your thesis + papers (including reading literature!), and stop. You won't get more done anyways, so enjoy the rest of your day guilt-free. It is a marathon, and the consistent 4-hour days add up. If you miss one day, don't do 8 hours the next day; just do another 4. Don't make more than 4 hours mandatory.
I completely agree. The only point where I fail at this is when I compare it to the 8 hour days I do once a week as a web developer (unrelated to the PhD). It seems so easy to power through the 8 hours and still feel like you could get more done. Then you go to uni, and if you manage 4 hours, it is a success. I always feel like I should be able to manage 8 hour days at Uni too, but of course it is a different kind of work which stresses different parts of your brain.
