That's a really good point you made about the connection between pushing beyond fatigue and then getting pain. Same with how extra sleep can reduce it.

I've found both to be true, although the extra sleep for me has to come in short spells because remaining still for longer than a few hours results in more spasticity and pain.

Its hard to know what is too much activity sometimes because energy levels and reserves can change from day to day. Things might feel OK while you're doing them and then once you stop, the body rebels.
Its a lot like when you don't drink enough water. Once you feel thirsty, you're already dehydrated. With MS and I think Fibromyalgia too, once you feel tired, you've already over done it.

Taking breaks every so often to evaluate how the body is doing (if it can get back up again relatively easily after sitting for 15 minutes), goes a long way.

With love, Erika