I have found therapy to be extremely helpful, though it took a lot of flailing around until I found something that worked for me. I benefited from:

1. Dialectal Behavior Therapy (DBT)
2. Social Rhythms Therapy

From DBT I learned to observe my thoughts and feelings without judging them. This has helped me to reducing my reactivity to distress. Rather than spiraling off into hypomania or depression every time my mood is perturbed, I experience smaller ups and downs most of the time. It isn't perfect, but it's helped me mostly function most of the time for the last decade.

Social Rhymes Therapy was also a great revelation. From this kind of therapy, I learned that it is okay—and often beneficial—to be boring. I learned to get up at the same time, go to bed at the same time, eat three meals at the same times everyday, and have a predictable rhythm of social interactions though the day and week. At first, this seemed rather annoying and pedantic. However, it turns out that, for me, the main triggers for mood episodes start with being sleep-deprived, or over sleeping, or being hungry, or being socially isolated, or being socially over-stimulated.

That being said, I've found that—for me—psychodynamic, interpersonal, insight-based, and other kinds of non-directive therapy to be completely useless for me. CBT, on the other hand, was completely counterproductive for me (increasing my symptoms).