Brethren, I do not regard myself as having laid hold of it yet; but one thing I do: forgetting what lies behind and reaching forward to what lies ahead, I press on toward the goal for the prize of the upward call of God in Christ Jesus. (Philippians 3:13, 14)
All of us have some fond memories of people we have known, things we have done, and our personal accomplishments. We also have memories of sin, disappointments and painful failures that we would rather forget. So it was for the Apostle Paul who was once greatly admired as a well educated, qualified and loyal Jewish religious zealot; Circumcised the eighth day, of the nation of Israel, of the tribe of Benjamin, a Hebrew of Hebrews; as to the law, a Pharisee; as to zeal, a persecutor of the church; as to the righteousness which is in the law, found blameless(Philippians 3:5, 6)
But then Paul met the risen Jesus Christ on the road to Damascus. All of his past religious achievements and accolades that he was once so proud of, he now considered less than insignificant, even sin and worthless rubbish; But whatever things were gain to me, those things I have counted as loss for the sake of Christ. More than that, I count all things to be loss in view of the surpassing value of knowing Christ Jesus my Lord, for whom I have suffered the loss of all things, and count them by rubbish so that I may gain Christ... (Philippians 3:7, 8)
If we dwell on them, our memories, both the good and the bad ones, as well as, our worries about the future, can retard our spiritual growth in Christ. No one wins a race by continuing to look back to where they have been. Nor is there any benefit in worrying about the future. Our future is, thankfully, completely in our Lord's sovereign hand.
Maybe you have heard this famous quote by Bill Keane; Yesterday is history, tomorrow is a mystery, today is a gift of God which is why we call it the present. Maranatha!