I have walked away from many things in my life. Some of them I've regrettted, but most of them I haven't. I've lost touch with people, burned bridges etc etc.
Despite being bullied, and knowing the pain that it inflicted, I have still bullied others. That it was a reaction to my own helplessness is not an excuse. It may explain it, but it does not make it right. That, thankfully, has been eliminated from my life. As far as I can tell. I now have better coping mechanism with a bully and that is to laugh it off and see them for the damaged person they are.
I do not regret divorcing my wife for her adultery and bullying of me, nor do I regret the marriage. Not just for the things it taught me about myself, but mostly because I have three wonderful kids as a result of it. There's still an element of bitterness about what she put me through and the way she behaved, but mostly it's in the past and will stay there. I know her too well to be permanently angry, and understand how she has been damaged by her own life to seek any kind of vengeance.
Do I still walk away from things? Yes. Are some of those broken contacts a mistake? Very Likely. Why? Because I'm not perfect. Sometimes I burn bridges too late, sometimes too soon.
If, like me, you have a faith and a belief there is something else after this physical life, an existence beyond death, then the life we live now is a lesson in how to be, an ongoing lesson in existence. That is only one reason not regret decisions. Another is that it's too emotionally costly to continually regret a past none of us can change.
I will continue to learn about myself, walk into, then away from things. By the time my life is over, I hope I will be a better person than I once was or could have degenerated into.