@gezzab33 has it covered I think.
I was brought up learning that I was always to be kind and helpful. If I could do something nice for another person then I should do it etc.
It's lovely in theory but doesn't factor in how many people are just nasty, grabby users so while I was never actually bullied I have been used and manipulated for my entire life.
I'm betting that you are lovely OP, we would probably be great friends and I would probably also be constantly telling you to stand your ground when you can.
I had one situation where the boss's PA wanted some personal work done. She asked me and I said I'd get to it if I had time.
A couple of hours later she's screaming at me in my office because I hadn't done it. Remember this was her personal shit, unrelated to our actual work.
She stormed out and I was right there after her, followed her to her office and got her told. I was shaking from adrenaline but my mouth was still going like a belt fed machine gun, it's like the "take no shit" me had totally taken over!
I don't recommend doing that at all, ever.... but by God it got me respected.
I still cannot believe that I did that tbh but I'm so glad that I did because I was a female in my twenties, working in a mostly male environment (Army) and had been viewed as just a skirt until I got all Rambo.