I think at the core we are all still that person we were at seventeen. After seventeen we still grow through experience and self examination (at least you do if you’re any kind decent human being), but all we can do after that is put on dampers or make modifications on what has been hard set since then.
You may realize your behavior in a certain situation is wrong, but it will always be your first instinct. If that behavior is non-beneficial to what you are trying to achieve in life and it burns you too many times you will have to control it and train yourself to stifle it or keep failing.
Over the years you accumulate a lot of checks and balances that basically exist to keep the reins on your adolescent self and prevent him or her from popping up and making a mess of your adult life.
That’s why people fuck up almost on a daily basis. It’s a very thin line to walk everyday, keeping track of all of your modifications and new rules you’ve made for yourself since high school while all the time that inner person that you’ve convinced yourself that you can’t trust keeps crashing around inside you demanding to be heard.