Today is not yesterday.
You cannot change your past by thinking about it over and over again, reliving details in your head, thinking about how it could have been different. Your past cannot be changed, but your soul can be cleansed and healed. In time God can take the past and make something good out of it, but the past does not change because it doesn't need to. If God needed to change the past to heal you he would, but he doesn't so it remains. When Christ came, died and rose he promised the forgiveness of sins and the redemption of the world and you are part of that world. But he did not come to change your past, he came to redeem it. The Beauty comes in seeing how his mercy takes the darkness and turns it into light. He loves you with abandon. He cares about the sins that plague you at night and the ghosts of people who turn your stomach over. He cares, but he will not change your past because he honors the free choices you made, but if you are willing he will take you out of your bad choices and bring you to a better, brighter Now.
Now. Today. This Moment. Him and You. You and the world.
You are called to the Joy and Mercy of Today.
"Though time is too precious to waste, it must never be thought that what was lost is irretrievable. Once the Divine is introduced, there comes the opportunity to make up for losses. God is the God of the second chance." - Archbishop Fulton Sheen