Plutarch has written an essay on the benefits which a man may receive from his enemies; and among the good fruits of enmity, mentions this in particular, that by the reproaches which it casts upon us, we see the worst side of ourselves.
My two secrets to staying healthy: wash your hands all the time. And, if you can't, use Purell or one of the sanitizers. And the other is hot peppers. I eat a lot of hot peppers. I for some reason started doing that in 1992, and I swear by it.