Regret is pointless and poisonous. Regret is different that owning your past mistakes. Taking ownership of your mistakes and resolving not to repeat them can be hard when you are bipolar. On the extreme side of either cycle things may be out of your control, but still, regretting them serves no purpose. The best you can do is to stay on your meds and keep seeing your therapist. That way you have a better chance of avoiding the extremes and having more to regret.