Personality is a funny thing. By the time you are middle aged, you cannot tell how much is nature, nurture, or the fruit of bad choices.
Doesn't matter. I have spent too much time trying to understand why I am the way I am, and not nearly enough time thinking about who God says I am. He tells me that all the old is passed away, and behold, the new is come. That's His Word. Am I going to put my word above His, or am I going to side with God against my own self-evaluation?
When I am bogged down in my own self-evaluation, I can veer close to despair. That is a sin and must be repented of immediately, and as often as I slip. It is the sin of unbelief.
Turning around a self-image of decades in the making is perhaps the toughest thing you will ever do. The devil will tell you (sweetly, compassionately) it is impossible. But you must do it, and there is grace for it. He does not command what He doesn't give grace for.
God tells us "put on the new self" (Ephesians 4:24). It is interesting that He does not say He is putting on the new self for us, so that we needn't bother. No, though He is the giver of our new life, yet He tells us we must put it on. We must take off the old thoughts and actions, like dirty clothes, and put on His new suit and walk around in it. (Say it out loud if it helps.) "Consider yourselves dead to sin and alive to God in Christ Jesus" (Romans 6:11). We are to do the considering.
Wait till you see how challenging this is when you get serious about it. But it is the way to live.