How do you find your energy limit before you crash?

been 18 months and still guessing at my window. last week i thought i had it figured out - 3 hours of activity felt ok. then tuesday i did the same thing and hit the wall at 2.5 hours instead, spent 3 days recovering. the rule is clear - PEM is real, pushing costs days.

but “pacing” means something different for everyone. some people log every activity in numbers. some listen to their body. some have a stable envelope.

mine shifts with heat, sleep, where i am in my cycle. so what’s the actual indicator that tells you stop here? not “listen to your body” - something concrete. does anyone have a reliable system for knowing your limit without going over?