One of the best things my first ME/CFS specialist (who didn't do enough for me otherwise) told me was to lay down in the early afternoon every day no matter how I felt. Eyes closed, no activities, but audiobook or music okay. If I was still awake and felt fine after an hour, I could get up. If I fell asleep, I should sleep as long as my body wanted, no setting alarms to wake up.
I was astonished at how well that worked. I soon realized this was a remarkably useful management technique for me. When my health was worse, I fell asleep and slept for 5-7 hours. When I was having a good stretch, I'd be up again in an hour having had a good rest and relax. It became my way of judging my overall progress -- as I improved with antivirals and OI treatments I had shorter and shorter naps and fewer and fewer days I didn't get up after an hour. It also helped me realize when I was trying to do too much as I felt better -- if my naps were getting longer again, I was doing too much.