For me I had to accept I can't undo the past - not one second of it. It is what it is.
That can take a while - both the accepting and the forgiving one's self.
The worst thing you can do is sit at home and mope, running movies over and over in your head.
I found service work was a great way for me to get out of the house and doing something meaningful. I needed to get out of my own head.
If volunteering in your community sounds like something you may be interested in I recommend it.
You could always get involved in local sports, the gym, or a hobby or particular interest.
The whole point is - the past is a closed book - but each new day is a fresh page - fill up every new page and before too long - you'll have a brand new book
D