I've never had COVID, as far as I know, but my health was wrecked after getting sick with influenza. My wife and baby got better. I got better, then got worse, then got better, then worse for longer...
It wasn't as bad as the original infection, but on bad days getting up and walking to the kitchen was a real challenge. I was in fairly good health before this, not obese, walked about a mile each day, and now I couldn't walk around my house.
That was 20 years ago.