Accountability in Mental Illness

[Cavernio]

Is someone with a mental illness responsible and/or accountable for their actions?
Are they sound of mind? Should one interfere with someone who has mental illness when they are self-harming even if the mentally-ill person does not want help?

I'm coming at this topic from the perspective of someone whose suffered from one my entire adult life, and who has recently really felt a paradigm shift within myself about this whole thing.
I recently came back from 10 days hospitalization where I have been put on mood stabilizers for the first time instead of antidepressants, and since getting out I have been delving into the realm of bipolar disorder.
I never thought I was bipolar. I have deduced for myself that I probably experience hypomania and rarely full-blown manias, but the depression is deep and the hypomania is more often than not a 'happy' manic. My past few months have been hell.

The paradigm shift I am developing, and testing the waters of fully adopting this way of thinking, is that I am not actually accountable for the worst of my behaviors when I have them because I am not actually in control. It's like I'm on auto-pilot.
I have never truly considered myself 'insane' as such though, until coming home from my hospitalization just recently. Now I think I am. And it's so obvious to me that it's coming from inside my body, and is not the world around me that triggers things. I experience body temperature fluctuations, mental tiredness that doesn't mesh with physical restlessness or vice versa, episodes of highs or lows can last hours to days, but never seem to have a reason for them.
But then one of the therapy groups that I went to while staying in the psyc ward gave a handout that was basically saying the best way to get through strong emotional experiences was to just allow them to happen, watch them as they go by. Don't try to change them. And it was sort of like the nail on the coffin lid for me. The best advice I'd heard the entire 10 days, the most helpful, was 'stop trying to change it'.
Why would this therapy, above so many other things that pretty much work with altering it or changing it somehow, work at all if it were not true that I do not actually have control over myself? Like, goddamn I've had problems for 15 years, and I keep struggling and trying to control and not let things take over, but nope, that doesn't matter at all.

It makes me actually yearn for days when institutions were around because at least then you weren't at all accountable for your actions. But now mental illness is like, being rested on the head and shoulders of the person who has it. Paradoxically this view is being held through while strongly touting the adage that mental illness is a disease that one is not in control of. But no, If they person wants it enough, they'll change, because they'll do enough therapy, try enough meds, they'll stick to it, they'll struggle everyday. But all I hear is, if they're sane enough, they can stave off the insanity. If they're not sane enough, they can't but are still being told to.