I'm not GP, but for me it's not about physical exhaustion, but a mental fatigue. I still can get in the zone and spearhead something for 8-10 hours non-stop, bu

I'm not GP, but for me it's not about physical exhaustion, but a mental fatigue. I still can get in the zone and spearhead something for 8-10 hours non-stop, but afterwards I'm feeling super lazy, like not wanting to think about anything, e.g. doing something purely mechanical.