I don't get sick, because I don't want to get sick. The most I get sick is the beginning of being sick, but I don't get the full-blown flu or anything. I haven't been sick-sick for several years like that.. well, except for December of 2005... but the reason I got sick then was because willpower was not enough to fight off sickness while my body and mind were just horribly exhausted from overwoking myself with school, work and schoolwork... and not getting enough sleep or food...
Anyway, take it from me, kids! Don't just give into cold when you feel like you're getting it. Fight the bastard! Fight it good! Say to yourself "I will NOT get sick, damnit!" It works for me.
Do get sleep and food and some medicine though. Take care of yourselves.