What lessons did you take from your regrets?
The biggest lesson is that life is too short to have regrets. I have to remind myself of this all the time. So I did some regrettable things. Can I change that? No. Time to move on then.
Another is that the past is in the past for a reason. Shit happened. A lot of it. Has it ruined me? A bit perhaps, but not beyond recovery.
So now, I try to do things purposefully and mindfully. I am not reckless like I was in my youth. This leaves less room for regrets.