I'm also bipolar; been diagnosed 8 years and symptomatic since I was a young child.
Slightly different to Kate in that I'm not asymptomatic with medication - every day could be a good or a bad day, relating to mood, anxiety etc and it's a balancing act. But, and it's a big but, you adjust and you manage and even if you spend every day balancing the symptoms of your illness, you cope and you learn to know yourself. You can be happy while still managing it. I am in such an infinitely better place than I was 8 years ago.
I also know many people who have come out the other side of clinical depression. It's definitely possible, with the right tools and want. The hardest thing is wanting to get better enough to put the effort in - it can seem like an impossible thought when even imagining getting out of bed fills you with dread. There's no magical answer to this other than to take baby steps, and to take it day by day. Therapy can be physically and emotionally exhausting and you have to hang in there, even if at times you're just dangling by a finger.
The answer to your question is that it can and does get better. But not on it's own. And not with no support. It's okay to lean on people. It's okay to have a bad day - it's not your fault. One bad day, or two bad days or twenty bad days doesn't mean a good day and a good life aren't on the horizon. It is a fight - but it can be won.
I hope you have or can get the support you need. Best of luck with all of it.
If you're feeling in crisis, please contact someone
http://www.befrienders.org/