Almost nothing is quite as fruitless as trying to attain a better past. Yet, it is something so many of us attempt to attain on a daily basis. What has already occurred has happened and no amount of regret is going to change it.
Regrets take myriad forms. All these forms share a commonality: they are profoundly useless. Regardless of if you constantly live in a state of "I wish I had just. . ." or if you tend toward the "if only I was given _____ I would . . ." you are doing yourself a disservice. Take responsibility for your own actions. Feel guilt, as necessary, but let it go.
Guilt is not a place to live but an emotion to feel and release. Feeling guilt is a good thing, it allows us to recognize and alter behavioral patterns. Harboring any feeling from the past will only prohibit you from fully experiencing the present.
When we dwell in these habits, we alienate ourselves from God. We are purposefully ignoring His commands to let Him be in charge and His desire to provide for us:
Therefore I tell you, do not worry about your life, what you will eat [or drink], or about your body, what you will wear. Is not life more than food and the body more than clothing? Look at the birds in the sky; they do not sow or reap, they gather nothing into barns, yet your heavenly Father feeds them. Are not you more important than they? Can any of you by worrying add a single moment to your life-span? Why are you anxious about clothes? Learn from the way the wildflowers grow. They do not work or spin. But I tell you that not even Solomon in all his splendor was clothed like one of them. If God so clothes the grass of the field, which grows today and is thrown into the oven tomorrow, will he not much more provide for you, O you of little faith? So do not worry and say, 'What are we to eat?' or 'What are we to drink?' or 'What are we to wear?' All these things the pagans seek. Your heavenly Father knows that you need them all. But seek first the kingdom (of God) and his righteousness, and all these things will be given you besides. Do not worry about tomorrow; tomorrow will take care of itself. Sufficient for a day is its own evil. [Matthew 6:25-34 NAB]
Acknowledge the past, but it is time to embrace the present and look to the future. We are not going to improve our individual backstories by wallowing in the past. Forgive-others and yourself. Move forward. Pray. Be kind.