There was a period of time when I played racquetball a lot. If you've played this game you know that the one safety rule is to never look back because the ball comes off the back wall so fast that it can smack you in the face and cause significant injury. It's wise to wear eyeguards even if you don't look back. Racquetball is a forward-facing game no matter where you are on the fully enclosed court.
Racquetball is similar to life in that way. To look back at your past mistakes and relive your failures will only cause damage. To dwell on the past can ruin your relationships, lower your self-esteem, and knock the confidence right out of you. To live in the "I wish I had done it different" or "Why did this happen?" will smack you in the face and cause you to have nothing but distress. On top of that, you can't move forward if you're looking backward. You can't undo your past, but you can do something about your present and future. You can only play the ball that is in front of you, not a ball that's in back of you.