"Never regret yesterday. Life is in you today, and you make your tomorrow." - L. Ron Hubbard
I've done things in my past that I regret. We all have. I've also wasted my time and energy regretting those things, rather then spending it on doing better today and creating a better tomorrow where I do fewer of those things I'll later regret. You see, the thing about regretting what you did in the past can not possibly do anything but bring you down and make it more likely for you to continue doing things you will regret, you see, there's this funny thing about the past -- you can not change it. So regretting it can not solve the problems of what you have already done.
So, what can solve it? Learning from your past, and using that to do better now so that you do not repeat those mistakes now, or in the future. That is an important life lesson I have learned, and learned well. Putting that life lesson into action is not always easy, in fact, it can be very hard at times, but the good news is it is quite simple. Learn from the past but do not regret it. Use that learning to do better from now on.