I don't believe in regrets. Until we have real time travel, there's nothing you can do about things we've done in the past. Can't get a redo.
What we can do is to acknowledge our mistakes and change things to keep from repeating them. And/or mend fences with those whom we've hurt.
My sobriety is far more about how much better I feel and how much better life is without drugs and alcohol than the bad things I did while drunk and using, or what my life was like when I drank/used. Yes, it was horrible, but positive reinforcement is more effective for me.
I had a problem. I solved it. Case closed.