I think there's some analogue between the sore body and physical tiredness after physical labour workdays, and the mental fatigue and dull brain after all-day i

I think there's some analogue between the sore body and physical tiredness after physical labour workdays, and the mental fatigue and dull brain after all-day intense coding. Both are quite unpleasant if they overwhelm you, but there are ways to mitigate both types of effects if you are in a position to manipulate your workday and/or your free time. Snapping yourself out of those states is pretty important IMO. I've had varying success with things like sport or general exercise, it really takes willpower to overcome sometimes though. Work in progress still for me.