I have a hypothesis where if a person does 8 hours of physical labour per day that breaks their body and if a person does 8 hours of cognitive labour per day that breaks their brain.

I believe that on average a cognitive worker might have 3 hours worth, in the best case, of "output" per day.

So, if you spend 8 hours today writing code, and an other 8 hours the day after because you are in a flow state that's cool but it will in turn lead to experiencing a few 0 hours days but the thing is we've been conditioned to feel anxious or are stressed by external factors to do "something" tangible on those 0 hour days were what we need is good and proper recovery time which we never get or allow ourselves to take because it is not acceptable.