I've had it since I was a kid, but like most people, I learned to deal with it. I've only had one major attack in my adult life, and that wouldn't have happened if I hadn't been doing something stupid to impress a girl.
There's a lot of great advice in this thread, there's only one thing I would add to it. Buy a good air purifier, none of that ionic crap, either. The ozone produced by those actually destroys lung tissue. Look for reviews on an asthma & allergy site to get a good picture of what kind you need. Then turn it on every night before bed, and remember to clean or replace the filters as recommended.
P.S. "Don't Panic!" Douglas Adams' advice is particularly suited to asthmatics. May he rest in peace.