I have LOADS of regrets! If i had it all to do over again, I would do things a lot differently because I have hurt people that i care about and I have made a few very poor financial decisions over the years.
But as things stand, in my here and now, I am happy with my life... i have a dog, i have friends, i have a boyfriend, i have a stable job (touch wood) that I don't actually hate, i have a nice car, a nice flat, and enough money to survive on (just!!)... 
My husband and I talk about this occasionally. We both made poor financial decisions in our early years (mine was massive student debt, compounded by credit cards to cover living expenses), and he took the scenic route in education while I took the scenic route in life! But then we wonder what the outcome would be now if we had done things "properly" back then. If I'd been in a better financial position, I might not have gone to LA, or maybe I'd still have gone but I might not have
left LA when I did, so I wouldn't have been 'free' to up sticks and move to England when my husband came along. Or what if I'd never even had that brain tumor, so I didn't meet my FIL back in 2002, and then my FIL couldn't introduce me to his son 9 years later... All of our experiences, good and bad, got us here, and here is good. We usually end these conversations with something sage, like, "butterfly wings, man".

I'm sorry people were hurt along the way, though. That is a valid consideration that I don't acknowledge as much as I maybe should. I was never deliberately cruel, though. I just prioritised my happiness and well-being over other's happiness (when I care for someone, their happiness brings me contentment, so my priorities aren't as selfish as this sounds). I acted on these priorities as gently as I knew how.