There are of course a million things that you can't do, and another million you shouldn't do, if you're flattened by Chronic Fatigue Syndrome. Here's my personal list, learned the hard way. These are gleaned from my early years with this CFS, before I'd learned--well, anything really--that could help reduce symptoms.
Not to say I didn't enjoy this stuff. I did. But each of them piled on top of the fact that I was already so ill and depleted I could hardly stand, let alone think, contributed to my demise. I'm still digging out.
1) Don't ignore signals saying it's time to rest.
Don't wait till you can't function. Vibrating, numbness, brain fog, dizziness, just to name a few, all bear a message. If you rest, some of them will ease up. Some will go away for awhile. If you barrel ahead, they'll increase until you're physically and mentally unable to continue and drop like a rag doll.
2) Don't go out visiting if you can avoid it.
I know you love your friends. But you're sick, and you won't get better staying on your feet. If you get so sick that you can't have visitors, you will really miss your friends, possibly for a very long time.
3) Don't agree to take over a Sunday school class.
I was a sucker and I knew it. But I liked being needed and I liked being asked. I told other overworked people they should slow down but I wasn't any good at it myself. I taught the class and my energy meter tipped further into the red.
4) Don't agree to lead a homeschool support group.
But they needed me! That's what they told me and that's what I told myself.
It was some of the best fun I've ever had. But you can't go to bed as a mindless zombie to regenerate, if you're hosting a meeting or leading a field trip. And going to bed as a mindless zombie was for a long time all that helped alleviate my CFS symptoms.
5) Don't do a monthly newsletter for anyone for any reason.
I did one for my church and one for my homeschool group. I found great pleasure in this.