I wish I could grab people and shake them ask them "why?"
I used to be you, or a least I used to be in situations like the ones you're talking about. I was 'stuck' for two years with a women who blamed me for everything that was wrong in her life, and hated me more than she ever loved me. I destroyed the interiors of two cars fighting with her. I punched holes through walls. She would seduce me so she could claim I was hitting on her when I'd say my feelings had changed.
I've destroyed friendships with people I loved, either by ignoring them or being just awful to them. I don't think I ever did it on purpose, but I did it.
I do not regret any of it. I regret nothing.
Regret is an excuse. I'm not saying this to accuse anyone and belittle anyone, please don't be offended. Life is an ongoing process, we can always fix what we have broken, and there is never any excuse for staying in a situation that is not making you happy. You do not owe the world anything, you do not have to be sorry that you exist.
There is always the harder thing that must be done before the hard thing becomes easy, but it can always be done. When you've made a choice you 'regret', deny yourself that comfort, apologize to whoever you've hurt, think about it long enough to really learn from it. Tell people how you feel. If they don't forgive, forget it . . . they don't owe you anything, either. But make peace with yourself. Be honest. Don't hide behind your fear . . . that is all regret is, fear.
If your lover doesn't love you, leave. It really is that simple. I've heard the bullshit about suicide threats - first hand - and there is only one thing you can do for someone so far gone that they don't want help from those who love them - deny them the power to hurt. Leave. It sounds cruel . . . I've had friends kill themselves and I've saved friends who've tried, and I'm telling you, you can sing and dance all you want, but people that far gone aren't listening to you, and aren't thinking about you, and probably don't even see you for what you are. Save yourself.
You will live somewhere between sixty and one hundred and twenty years, and then you will die. You may enjoy it if you wish, or you may hide from joy. I did it for years. Now I don't; I choose to enjoy . . . to learn from my mistakes, to take responsibility for the things I do, to fix my mess ups, to leave bad situations.
I do not respect people whining about regrets. I do not read sappy poetry about the consuming regret of living twice. I do not respect people admitting their terror, and reveling in the awful questioning of self image, the dirty feeling of self pity, the malaise, and the fear of the faces of those that have been hurt. When my friends give me these stories about the things that they regret, I get angry with them. I want to shake them, and tell them to smile, and make them realize that the world is not a terrible place. | 
