But Jesus said to him, “No one, after putting his hand to the plow and looking back, is fit for the kingdom of God.” (Luke 9:62)
Jesus warns us that if we look at the past, this causes us to fail at accomplishing what we should for Him and His Kingdom. Jesus uses the plowman as an example. Does a plowman look back when he's plowing, and if so, what happens? If he looks back, then the plow goes off course and fails to continue fulfilling its purpose. A plowman always looks forward to completing his task successfully.
If we long for what once was or regret what we did wrong, this uses up our energy and takes our focus off of God and His purpose for us. It's hard to forget, and I don't believe God wants us to forget. He wants us to learn and keep moving forward despite any challenges that come our way. He does not want us living in the past that will not change, no matter how hard we stay there. Some of us may not want to leave our comfort zone, and it's too scary to think about changing. There is no growth without change. Christ wants us to continually grow our knowledge, love, and our relationship with Him. If you're struggling with letting go of the past, go to God in prayer. Ask Him to give you the strength and ability to move out of the past so that you can continue to grow your relationship with Him and be an active participant in building the Kingdom of God. Let the love and hope of God keep you moving forward to eternity, where you will receive your rewards for faithfulness, obedience, and service.