Things that get me down

Things that get me down are both now and in the past. And the things in the past hurt worse - I think that is strange but true.
What hurts me now is living alone. Not having a partner to share life with. Knowing that having bipolar significantly inhibits my ability to relate in healthy ways. I'm not social, don't enjoy talking to new people and am still somewhat moody and depressed. Making a relationship work wloud be almost impossible for me right now even if I found someone... This makes me very sad, not to mention lonely.
What hurts me from the past is memories of things gone wrong, and there is an unending list of them. Almost 50 years worth. And the memories surface continually throughout the day. It feels like I am beating myself up with these thoughts, they are very painful and I can obsess on them seemingly without end.
My friends say, think about the positive things, forget replaying those old movies in your head. Not so easy to do. I have more bad memories than good ones by a margin of 100-1. And I mourn the past, wonder why things went bad, knowing I played my part. I wish I didn't dwell on the past so much, it's really painful.
I don't know how to get control of my thoughts. To get rid of the painful ones. To stop replaying old movies of things from the past. I can try but... maybe when I get on the right meds it will be easier. I can only hope...