One important lesson: Life is not a rehearsal. No chance to do it right the next time.
But that is not bad news for you. It means that you can't change your past, but have COMPLETE freedom to choose your future. Decide what you want out of life. Write it down. Write it down everyday. And every day as you write down what you want (let it change, if you change your wishes and your mind) you will begin to realize that the only thing stopping you from being and doing exactly what you want to be and do is your REFUSAL to let go of old flaws and old obstacles. It is not the past that hinders you, it is your desire to inject the past into your present and future.
Even more importantly: Pray, and ask God to help you see how this past is meant to help and teach you now. Try to see if any good has come out of this past, even in unexpected ways. It is strange, but if you start to do that, sometimes you begin to see that even bad things can turn out to be blessings in disguise. I do not know what you went through, but think about it.