Don't worry, we're not out to convert you into vegan marathon runners and gym junkies! How you maintain your health is entirely up to you. We will point out a few things, though.
You can't sing well when you're tired or sick. Your concentration and your energy level suffer. Not only that, coming to rehearsal with a bug puts your choir mates at risk. Stay home, take care of yourself and get well. While you're recuperating, you can memorise a few songs too, right?
Stay aware of your body. Stand when you can, sit when you must. Powering through because "the show must go on" is an admirable goal, but if you collapse in the middle of it, the show stops anyway.