My genetic pattern seems to show more debilitation in the 20s. Unfortunately, some people don't recover from the damage (to health and career) done in that phase. I seem to have made it through the worst, though.
It was in my late 20s that I learned to live with an unstable mood. Sometimes I'll have a panic attack (10 minutes of extreme adrenal excitement for no reason) or a depression attack (an intense 2-4 hour bout of depression that, while leaving me exhausted, seems to leave no lasting mark) but I take a zen approach. Yes, this is actually happening, and it's just emotion. Easier said than done, for sure, but it's an ongoing practice.
Panic attacks I think of as a stern, somewhat obnoxious teacher whose motivations I haven't figured out yet. What makes panic scary is that it can imitate pretty much any physical disease. Phantom smells, visual flashing, chest pain, balance problems, paresthesia, vertigo, vomiting, blurry vision. I've had pretty much all of that shit. Over time, you learn that it's not dangerous. Then it becomes an annoyance (like a traffic jam) rather than a source of terror.
I don't think of myself as disabled by it. Most creative people are on the bipolar spectrum (although two thirds are probably sub-clinical). I don't lose work time to it, and my "never flake" rule keeps it from being too disruptive. I think of myself as traveling the same road as everyone else, but in winter rather than summer. And there are things you can see more clearly when the trees are bare and the air is crisp.
The #1 thing you can do to at least not help drive yourself deeper into depression is to learn cognitive therapy, which nowadays has a "behavioral" aspect added to it that I'm not familiar with (this is the CBT Michael refers to in his message composed at the same time as mine). Buy this book; I keep extra copies to give to people: http://www.amazon.com/Feeling-Good-The-Mood-Therapy/dp/03808...
If you're truly bipolar, there's no substitute for a doctor's care as well, you'll probably need a mood stabilizer, of which there are many varieties from the "gold standard" of lithium to modern atypical anti-psychotics.