I get a lot of extra comfort from the knowledge I will continuously improve. If I keep the stress slightly to low I wont grow as much but the recovery window will be smaller. If it is slightly to high recovery takes longer and the speed of progress is less than ideal.
Needless to say: Nothing is as important as eating properly and getting enough sleep.
I'm able to do idiotic amounts of work and enjoy it but if I explain the above to people who know this they never seem to understand. It hurts seeing people ruin their health with work but I keep seeing it.
After lots of fiddling I'm 99% sure that a 3 day work week is ideal to fully exhaust ones abilities. (If I'm not recovered fully in 4 days I do slightly less the next week.)
I use to think it depends on the job but if the work cant be done any faster you just make longer days. Something like 1 day 16 hours, 1 day off, 2 days 16 hours, 3 days off. If I work 6 or 7 days 8 hours per day I do roughly 1/3 per hour.
As one coworker of mine "famously" said when he was again asked to work extra shift: When do I live?