When you have a hurtful past from childhood or any other time, it doesn’t just go away when you become an adult. It sits within us and when we are ready it comes up so that we can work through it. As an adult you have grown and the inner self is aware of the perfect time to bring your past into consciousness. This is a good thing. Our inner self knows when the best time is. We may have had insights and are stronger that created the valve to be opened. You are given a chance to heal if need be.
The important thing to remember when your past comes back to your mind, is to learn, understand, accept, let go, and move on from the thoughts and feelings of the past. Little by little, you will be able to let go a little more and a little more when it shows itself and then one day you will find that you no longer feel attached to the past.