Don't freak out - you don't need to change your life completely. Matter of fact, you just need to take the same precautions anyone should take. Wash your hands often, use hand sanitizer when a sink is not available, avoid people obviously contagious, don't eat/drink after sick people, etc. Just common sense stuff. And definitely DO get vaccinations like the flu vaccine - just don't get the nasal version.
I've been on immune suppressant drugs for the last 5 years (Remicade, Humira, now Cimzia) and I haven't gotten any sicker now than before. Matter of fact, thanks to my disease being under control due to the meds, I find myself healthier. I've been sick once with a non-Crohns related issue and that was strep, about
2 years ago.
I work with the homeless population and children on a regular basis in a church. We all take the same precautions to avoid passing around illness to ourselves and those who enter the building and I've had no issues. I even vacation to a huge germ pool (Disney World) at least once a year and travel for business on airplanes. It's no biggie.
I don't change my behavior. I hug those kids, wipe snotty noses, shake hands with the man on the street, touch the doorknobs, etc. I just wash my hands frequently and don't touch my nose/mouth until I do.