i can relate, but can't put it into words too well, like you it is very confusing. What i try to do is make the most of the good days, though often i over do them and exhaust myself for days afterwards! so my advice is take these days as a gift, but do not go crazy trying to do too much, take the opportunity to plan what you want to do, make a list and if the feelings go you will have your list to remind you what you want to do, make notes on the how to do if you feel you may not know later.