Dwelling in the past prevents doing something in the present.
Too often we get distracted by what is outside of our control. You can't do anything about yesterday. The door to the past has been shut and the key thrown away. You can do nothing about tomorrow. It is yet to come. However, tomorrow is in large part determined by what you do today. So make today a masterpiece. You have control over that.
Promise yourself you will talk health, happiness, and prosperity as often as possible. Promise to think only of the best, to work only for the best, and to expect only the best in yourself and others. Promise to forget the mistakes of the past and press on to greater achievements in the future.
Don't be afraid to fail. The greatest failure of all is failure to act when action is needed. Use the information that you've acquired in the past through the experiences you've had and act with self-control - but act.
I like to spend time in the past, with the things that have been important to me.