Yet, the Blessed Truth is that we no longer are who we were then. There is nothing to be gained - and much to lose - when we cannot forgive our younger self, a self who did not have the knowledge, experience, sensitivity and depth that we have now. And, we've gained all our current good personality and soul strengths because we learned from those mistakes we made in the past! Sometimes we criticize ourselves for not acting with heroic virtue in those past times. Yet perhaps at that stage of our life we were doing the best we could with the amount of time and energy and insight that we had.
If we are truly bothered by and grieving about a sinful deed from our past, or we cannot get free of guilt, we need to talk to a priest or minister. The glory of the Catholic Sacrament of Reconciliation/Confession is that we can verbally lay our burden down, hear the priest say the words that God and His Church forgive us, and receive a torrent of grace, new life for our souls.
Yes, we usually develop our greatest wisdom and compassion through experience and/or age. Yet, look at the life of a rose: it reaches its fullest, most beautiful bloom and perfume just before it begins to die; yet at every stage of its life, from tenderest bud through the gradual unfurling of its petals, it is alive and radiant with beauty, capable of inspiring our wonder and awe. God looks at us with wonder and awe at every stage of our life, because always He is doing something new in us and He finds us radiant with beauty.
God wants us to neither harshly criticize ourselves nor compulsively over-praise ourselves. God wants us to lie pliant in His Hands, both trusting that He has worked through us in the past and trusting that he will work through us in the present and future. He alone sees the totality of who we are - He loves us, and He created us with every gift and flaw, and He sees all the newness of life that our flawed goodness can and does produce.
We are limited human beings, yet His plan for His world is limitless, and He fulfills those plans by interweaving the lives of millions of human beings. Certain bad or flawed decisions that we made in the past could never thwart the plans of His Heart; He always works through us, for us, in us, with us, and in spite of us!
We cannot take ourselves either too seriously or too frivolously then. When we start to think too much about the past and our past mistakes, we can always ask ourselves "What did I learn from that?" Fr. Richard Rohr says "...like all good parents, God desires...the flourishing of what God created and what God loves - us ourselves. Ironically, we flourish MORE by learning from our mistakes and changing than by a straight course that teaches us nothing." ("The Naked Now.")