If I get sick, which I don't often do, or if my energy levels drop, I know myself and often what I need to do is just stop and be, and to get plenty of sleep. No rushing, no expectations.
I am happy to make tomorrow, Saturday, my day of doing, as I am sure that by then I will be feeling refreshed and energised. I am fortunate that I have that flexibility being self employed and apart from the "fur whanua" no dependents.
It is useful to know when to push yourself further and when to let go. When was the last time you "Let go and just be" , if only for an hour or so.