Everyone gets sick. This leads to a lot of staying home and having time on your hands. You could just rest and try to feel better, or you could put this new found time to use. After all you are sick, and no one is going to be around. With no bullshit from other people to deal with, you can finally get some things done.
Got someone in you hold a grudge with? Why not use your sick time to plan your revenge. You have a couple of days here, you can at the very least lay out the broad strokes. While you might not have time to iron out all the details, but you could get half way there. You could even use your ailment as part of the plan. You likely have many, disgusting, things oozing out of you; why not use them to your advantage? Of course, some people aren't in to revenge.
If you are sick, you are home, and if you are reading this you have access to a computer. Why not do somethings online? Maybe start a new hobby. You could take up bully or stalking someone on the internet. It doesn't need to be someone you know, it can be someone picked at random. Some people say it should be crime, but it isn't. If you are very good at it, you might even drive someone to suicide.
Now some of you might want to be more practical. Everyone has a backlog of something. Could be books that need to be read, movies that need to be watched, games that need to be played, or some other such thing. The daily grind often leave you with little time for you interests, why not use sick time to work through some of your backlog. disease
Being sick can be an annoying experience, but you can do things to make it more worthwhile. Or you could just sleep. Then again, why sleep when you could be having a good time?