If I looked back at my past lunacy, wasted time, etc I would be in deep doo doo Paulos. I drank and drugged for 28 years.
That is why it is critical to live in the present. We have to acknowledge our past, make amends where needed, and move on.
When I find myself stuck in dwelling on the past, I take action now to change the direction of my thoughts. Gratitude lists really help, as does going to a meeting, or calling a friend in sobriety to help snap me out of it. I also find logging on to SR and reading posts from people struggling, and offering my support takes me out of my head right away.