I have some that I could have changed and some that I couldn't.
I wish I'd been a better mother. But I know my strengths/weaknesses and I'm just no good at it. It isn't in me.
I wish I hadn't moved to the part of the country I live in. This WAS within my control. But I'm trapped by house prices now.
I had a fab job 10 years ago that I wish I hadn't left. That was a bad decision.
Equally, I had a hugely well paying job 5 years ago that could have changed the trajectory of my life, but it meant only seeing family once or twice a year. It wasn't sustainable. But...
Wish I hadn't bothered with any of my LTR. They were all crap in one way or another.
I've lost sight of key concepts at work a few times. I know the theory really, but I've let emotion get in the way, when I absolutely shouldn't have done. I regret it and I'm 100% to blame for it. Didn't lead to dire consequences or anything, but I'm still ashamed now.
Nearly forgot! A huge, huge, huge one. I went virtually no contact with my mother for the last 5 years of her life. She badly hurt me (and had also been a not great mum), but I really wish now I'd made more effort to at least stay low contact. I do understand her/her life and know she was a victim of her past (as we all are). I cringe now when I see others going NC with their families. Not saying everyone doing it is wrong. But some people will end up with the regret I carry. And it's huge.