Have you ever thought about what you would want to experience again or do over if you had a time machine and could travel to the past? We all have that one thing we would do again if we could. It's our way of looking into the past and righting the wrongs we've made. Unfortunately, it's impossible to revisit the past. But should we worry about the past anyway? Is it a waste of time to dwell on something out of our control? Here's why I, personally, think about the present and future, not the past.
One of my mentors once gave me very simple advice one day. He said, "We can't worry about what we can't control." You can put many things under the umbrella of "things we can't control" as humans (e.g. the weather). On an individual level, there are many things that are out of my hands, and the past is one of them. The past is good for learning from mistakes and successes, but not much else. When I dwell on the past, I lose touch with the present and future, things I can control. Dwelling on the past hinders my growth as a person and prevents me from improving and building on a past decision.
When I think about my life, I rarely think about what I should've, could've, or would've done. That thinking tends to turn into regret and regret turns into self-hate. The past is over with, and I can't bring it back. But what I can do is make sure that whatever I'm faced with in the present and future is met with a better decision than the decision made in the past.
Thinking about what you could've done in the past is wasting brain power. Your current situation needs you. Your future needs you; your past doesn't. You left the past where it belongs, now it's time to move on because life is all about moving forward.