You want to be happy? you should first learn how to let it go

If it’s history, let it be history.

Life's not perfect. Some loose ends may never get trimmed up and tidied.

If you want a revenge, don't hold it. It poisons you.
Either you just let the grudge go, or make him chary.

Don't close the door to the past, leave it open and let it go.

Let it be then let it go.