why do people treat me like dirt?

for example i helped my mother through cancer, helped her move house, helped her emotionally through my parents divorce, buy her gifts on mothers day and her birthday of course, picked her up when her car broke down.

But instead of loving me she decided to make my life a living hell and use me as her personal punching bag for verbal abuse and once she was screaming the house down saying she wish I was never born.

Another example is on a group tour to australia I was bullied by everyone and ganged up on. I was being really friendly and trying to make friends but they all hated me and ruined my trip I paid thousands for.

Another example is my previous landlord I helped her with the gardening a few times and looked after her dog a few times and I did some chores to help her like cleaning the carpet. Then she made my life a living hell and I ended up having to live in my car for a few months because I can't go back to my mothers.

I sit here staring at the wall and I just can't wrap my head around it. I've always been friendly and kindhearted so why would you abuse someone who is helpful and kind to you?

Now my mother expects me to forgive and forget.

I don't understand this world.