"That's just who I am," is a Bullshit, Made-Up Narrative.
You know that saying “When someone shows you who they are, believe them?” Well, I’d like to alter it to read, “When someone shows you who they believe they are, believe them.” Because we are not etched in stone.
Couldn’t you just own the shitty thing you did and try to be less shitty in the future? Couldn’t you use it as fuel to go around spreading some non-shittiness in the world? If you fuck up, own it, apologize, and move on.