Without doubt, the worst thing we can do is regret about our past.
The past will always appear in both the present and the future. If you regret of certain things, you will suffer when they come to light again.
Learn to overcome it and accept it, so when someone tries to hurt you with it, you can look at them with your head held high and say: I do not regret about anything.
I feel happy now because I know:
I DON'T REGRET ABOUT ANYTHING.