How often have you reflected on your life and experienced regret? I've done somethings in my life that I am not too proud of, made some bad decisions (along with some pretty good ones).
The idea of regret hit home for me years ago when I reconnected with and old girlfriend from college. Through a series of bad decisions and life circumstances we didn't end up together. We discussed the twists and turns of our relationship. She blamed me for some of her bad relationships. If I hadn't been an idiot and made her mine she wouldn't have had to experience those things. She failed to recognize the bad experiences she would have had with me.
I doomed our relationship when I failed a test she gave me, a test I didn't know I was taking, but one I probably would have failed anyway.
We spent a lot of time wondering about what our lives would have been like if one or two decisions had been different. Then we started talking about our current lives, the things that happened because we didn't end up together. She became a lawyer, got married, had two beautiful kids, later became a grandmother. I got married, had three exceptional children (with a few faults but we are working on those). I have a good job, a nice house, a few good friends, all in all a good life.
It was fun to fantasize about what might have been, but for the fantasy to become real we would have had to sacrifice the lives we have lived and all the good things and experiences we've had.
So I don't really have regrets other than wishing I had treated certain people better, that I had been kinder in one particular bad breakup, that I had been a better friend when someone was going through a hard time.
I am the person I am because of the experiences I've had, because of my relationships and all of my decisions, both good and bad. everything has brought me to where I am now.
What's my point? Don't dwell on regret. Don't feel bad for what might have been. You are who you are because of all of it. Everything has shaped you into the person you are right now. If you don't like things you've done consider them teaching moments, examples of what not to do again. Acknowledge your mistakes, apologize if you feel the need, but stop beating yourself up over them.
Be a better you with all the life experience you have earned. And if you have a friend or loved one who is dwelling on the past let them know it's okay to let it go.