Ohhh man! I've had my fair share of those
Ugh! I'm so sorry, Scandic! When I have one or more of those days, I only do what I absolutely need to do. Feeding the cat, feeding yourself (the healthiest you can manage), drinking as much water as you can -within reason of course. If you are in a lot of pain (preventing you from moving much) or extremely exhausted, you won't want to drink quite so much.
Don't try to do things that aren't necessary, if you can get away with it. If you can stay at home, do so and rest as much as you can. The one thing I have always been able to count on with my infections is that things will
change - frequently!
Hang in there!!!