I'll probably pay for this post in the form of getting some nasty crap going around out there, but one thing that I have started doing is making sure that I have clean hands before rubbing my eyes, going to the bathroom, or consuming food or beverages. This really applies to messing with any orifice in the body.
Before doing this, I would get a cold or whatever usually a few times a year. Now, my sick spells are fewer and farther between. Up until a few weeks ago, I hadn't been sick for almost two years (knocking on wood!). A remarkable feat when considering having a young 'un living under the same roof that brings home more than his share of bugs! It really has made a difference!
Loose Nut, hope you get well soon!