How do you really heal from past trauma

As I sit here I reminisce my younger days how I was bullied all the way into high school and even after that, I never graduated but got my ged and even changed my name . it was so bad and then as I reached my adult days people take advantage of me . Iv come across people making fun of me, taking money from me abusing me emotionally. I dont get it, I’m so nice and I try to be stern especially nowadays I don’t even look at people in their face , I just made bad decisions all around . I just want to feel strong so now can take advantage of me or push me around. Nowadays people are a bit more careful around me because of my demeanor, I’m just I hate that I let people do that me , im tired of being such a nice person. I know that comes with time and working hard to earn respect.