I can think of a few things that I regret, and some of those do suddenly pop up again inexplicably, out of the blue, to haunt me again: not sure that I can really say it's an increasing tendency with age though (and I am older than you, meself).
On the whole I have managed to rationalise and come to terms with these incidents to myself, or friends have helped, e.g."It's not you that's got the problem, it's that other person". And, of course, you can't turn the clock back and re-wind these events.What's done, is done.
If I were to put a song to it, it would have to be:
"I'm just a girl whose intentions are good,
Oh Lord, please don't let me be misunderstood".