You don't know what your life would've been if you did something different, could be worse, could be over as was pointed out above.
I made some MAJOR mistakes as a teen, screwed my life up pretty good for a while, of course I regret it, wish I'd kept my life together for that year when I got involved with the wrong woman, and the wrong crowd.(Banditos)
But if that hadn't happened I never would've had the experiences I've had, never would have learned the lessons I did, never would have enlisted, probably never would have met my wife.
Bottom line is even so I made some mistakes, I never did anything I can't respect myself for, that choice to do the right thing when it came right down to it led me to some serious problems with an injury and legal problems even, like I said really screwed my life up good.
But I like the man I am today, I'm not sure I'd be me if none of that ever went down. It was a defining event in my life.
So do you like you? That's the real question. If not make a change and be the man you want to be.
If you like yourself the way you are you can't have any regrets, your mistakes define you.