Being capable of continuing does not always mean continuing is intelligent.

You can nearly always keep going, which is exactly why endurance is a poor guide. The question is not whether you have another hour in you but whether that hour will produce anything worth what it costs, and by the time you are asking, the answer is usually no.

Watch for the point where your work starts needing to be redone. That is the boundary. Stopping there is not weakness, it is noticing that the returns have gone negative.