"Those who do not remember their past are condemned to repeat their mistakes."
As with most other things, it's a matter of moderation.
A Christian prayer comes to mind..
"God, grant me the serenity to accept the things I cannot change,
Courage to change the things I can,
And wisdom to know the difference."
You can never get rid of things that happened in the past nor can you your hopes for the future. And neither should you.
The key, and the hard part, is figuring out which things from the past that are still relevant for you to learn from and which things that will only bring harm.
This isn't something we can just whip up just like that, but something that takes a lifetime to really get good at.
It is something to learn as you get better and not a prerequisite for getting better.
This. As you'll all know, its not really possible for the human mind to just go 'okay its over and done'. What you need to do is find peace and resolution with what happened before. When you continue to ruminate over a certain thought its because theres still something there you havent resolved. You need to get to a point where you've realized what went wrong, how you'd do it better, and finally forgive yourself. The problem is sometimes we get stuck because we dont know the answers to those things...which is why they continue to plague us. But once you resolve those issues, things naturally fade into the past because we are truly done with them.