Well it depends how sick you feel. Personally, if I only have a cold, I prefer working (from home) over hanging on the couch and watching Netflix all day long. If I'd have to come to the office I'd report ill though, also because I don't want to contaminate my colleagues.
Rest benefits you and your employer. Working while ill is a sure path to burnout. Burnt out employees are less productive and more likely to quit.
It’s okay to not grind 25/8.
Note that doing nothing does not necessarily mean that you relax. Working at home at your own moderate pace might make you recover faster. But again, what works well for somebody might not work well for someone else.