Trying to Understand

I am (or was) a significant other for 8 years to a man with Bipolar. I say "was" because he has recently died from, in my opinion, lack of medical care (but that's another story). Anyway, I am trying to understand some things and would like to hear from people who have actually had these feelings, which is why I'm not posting under the SO section.

As is common, our relationship was a roller coaster from the start and I think I handled things abouy as well as they could be handled. My ex cycled into mania the last week in March like clockwork and he normally evened out around Labor Day. He was medicated, but I'm not sure how effective it was. He was hospitalized at least once every summer, sometimes more. He rarely left the hospital stable and it seems to me he normally came down when he was ready.

Our relationship was romantic for the first three years. When manic, he would break up with me about once a week, I never fought this and he would generally return a day later saying he didn't real mean it. Eventually, after a particularly fun weekend together, he called me the next day and said the relationship wasn't working for him and broke up AGAIN. This time I made it stick, although in his mind it was me who broke up with him. We remained friends and I saw him and we did things together many times after this point.

Here's my question. When manic, he was never happy manic, he was irritable, grandiose and downright emotionally and verbally abusive. He would call me 6-10 times a day and leave terrible voicemails using the worst language possible, calling me names, leaving no aspect of my personality, life, or actions untouched with his invective. I never fought with him, I just told him I would talk to him when he could be civil. He screamed at me on the steet one time to the point where other people stopped to help. I never once engaged. If this behavior started when I was with him I would immediately leave, letting him know that we could talk again when he could do so in a socially acceptable way. He only did this when manic, and he did it to all his friends and his mother, who was very supportive.

From corresponding with other SOs of bipolar people, I understand that this is not unusual in mania. But what I want to know is, "What is going on in his mind when he is acting like this?" If he believes all this stuff, why not just go away? A good bit of the stuff he would say to me and accuse me of really wasn't relevant to me, it was more a projection of his own issues.

For people who get abusive when manic, what is going on that is causing this? What are people thinking. I never really let this bother me except at the very beginning, but it did get wearing. Now that he has recently passed and I'm not devoting all my energy to dealing with the behavior I have the time to try to understand it.

Anybody willing to share?