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.
The apostle Paul, who wrote about half of the books of the New Testament, says, "One thing I do, forgetting those things which are behind and reaching forward to those things which are ahead" (Philippians 3:13). He was saying, "The most important thing that has helped me to be successful is to let go of the things that are behind me. I don't look back. I don't go back to my past mistakes and relive my failures." He knew that God will take what the enemy meant for evil in our past and He'll turn it around and use it to our advantage. God has a plan for your past, but He can't work in your past because He works in the now!
It's easy to let the past hold you captive, whether it's through anger, bitterness, or unforgiveness. You can press past anything that keeps you looking back by doing what David did. He said, "In my distress I called upon the Lord…and my cry came before Him, even to His ears…. He brought me out into a broad place; He delivered me because He delighted in me" (Psalm 18:6, 19). If there's anything from your past that's keeping you from your dreams, call out to God and ask Him to help you move past it. He will bring you into a broad place because He delights in you!