As human beings, we are not born perfect. We will occasionally screw up from time to time. But the most important things about making mistakes is owning up to them. Why? Because it's a sign that you're sorry for your faults and want to become a better person as a result. Learning from your past mistakes is one of the oldest lessons you will ever learn but it's an important one nonetheless. If you don't learn from your mistakes, you will never improve. Which is why you should always learn from your mistakes, even if they happened a long time ago, you should still learn. And don't deny your past mistakes, because doing that shows you still haven't learned. Be honest, be truthful, be mature. When somebody says, "Hey, didn't you used to do something like that a long time ago?" Just say, "Yeah, I did. It was a stupid of me to do that, and I've learned from my past actions." If you've hurt someone in the past, you should find a way to apologize to that person, acknowledging what you did was wrong, and assuring that person you will never do something like that again. It's not easy, but it's very possible. I know I've made some mistakes in my life, but I also know that I've become a better person by learning from them and trying to be a better person as a result.