For me, it's mostly meds and support from my family and friends. I know I always complain about my family and friends not understanding me, but knowing that I can lean on them if all else fails gives me strength. Therapy is not a typical option here so I haven't tried it. I just follow my psychiatrist's advice and try to manage things on my own. I was in quite a mess my first few years, but little by little, I learned how to see signs of going up or going down and how to deal with them. I read a lot of things about bipolar disorder online, but this is the first time I actually joined some forums after more than 10 years. I've never really talked to other people with bipolar disorder in person.
Oh, and another thing that helps me a lot is my teaching job. I always try to be stable for my students. Of course, it's my main source of income, but I also care a lot about them and about doing my job well.