It's almost like this whole "immune system" thing actually works...
ever? I know people say this all the time, but are you sure, you have never had the flu?
I generally don't get sick. I catch a head cold sometimes during the season but again, it's usually pretty mild and gone the next day.
When our kids went to preschool, my wife and I had colds frequently. Teaching our kids the basics in hygiene at 3 years old is hard enough, but putting them in a germ hostile environment exposed them to all sorts of new germs, the result being a minor blip on their uber-immunity systems and full blown cold for ourselves.
My aunt never had the flu and was barely ill most of her life due to similar behavior. A couple of years ago she caught the flu from someone and it put her in hospital for a few days and then kept her in bed/at home for about 3 months (all told).
Everything basically hit her at once.
With that said it might be you simply have a naturally higher immuno-response to viruses. I tend to get simply mild colds when the rest of my family are in bed for a week with flu :)