For me, the diagnosis was a relief. I wasn't diagnosed until I was 30 and had crashed into disability from work. Yes, it was a little sobering. I was no longer "just depressed" or "really irritable" or "having a hard time". But I also had some answers to the big picture, and some hopes of getting better. It also shed some light on some of the crazy things I did when I was manic and helped me forgive myself for them.
It sounds like you caught it early, so this is good news. The medicine can definitely help, though it may take some time to find just the right mix for you. Lifestyle changes are a big part of managing this illness. Getting enough sleep, avoiding drugs and alcohol, eating well - all things that we should be doing anyway, but are even more important for people with bipolar. Something that I found very helpful when I was first learning to manage this is mood charting. There are pre-made mood charts you can find online that can help you track how you're feeling from day to day. You can include things like medications taken, hours of sleep, stressful events, your menstrual cycle (if you're female) - they can all give you clues over time of how you tend to cycle and what particular things you need to watch out for.
Having someone to watch your back for you is also good. Sure, we know when we're feeling crappy and depressed...but when we start to get manic...that's another story. I try to watch for it and use corrective measures if I notice it coming on, but sometimes I miss it. I don't know about anybody else, but when I get manic, I lose all objectivity. I feel fantastic and don't anybody dare tell me I'm getting sick, lol.

If left to my own devices, I end up communicating directly to God and getting personal messages from the radio. Or having sex with people I shouldn't be. Or a dozen other crazy things.

So, having someone there to say, "hey...I think you're getting a little hyperreligious..." or, "you're not sleeping...let's call your doctor" can really be a lifesaver. So, educating not only yourself, but others close to you, is also important.
Bipolar disorder doesn't have to derail your life. It can be managed. You can still work, go to school, have a family, etc. You just have to be more mindful of how things are affecting you and know when to cut back a bit. There may be some setbacks, but you can come back from them. There are many successful people who have bipolar disorder. Actors, writers, politicians, doctors...(and lots of regular people too, lol).
There is a good magazine called BP Magazine.
http://www.bphope.com/
This can be a good source of insights and success stories to help inspire you and help you on your journey through life with bipolar. It doesn't come out nearly as often as I would like (I think it's only 4 times a year), but it is worth the wait.
Hang in there. Work with your clinicians. Keep talking to us. You'll get there. Welcome to PC.