Why am I so nice? Please read...

I’m 22 years old & all of my life, I’ve been known as the super nice girl. Which I am, I’m nice to everyone that I come in contact with. I was raised to be that way, which everyone should be. You don’t know what someone is going through behind closed doors. But, sometimes I feel like I am too nice. My bitch side has for sure come out when it needs to, (which I am proud of), but at the same time, I feel like people think that they can just walk all over me. I honestly don’t want to be this nice ass person anymore. I want people to be intimidated by me & know not to fuck with me. But at the same time, I have the sweetest heart & will do anything for anyone. Has anyone felt this same way & has any advice for a young adult like me?