Why do people always find a way to make things worse

I always try to be as nice as possible to people I meet and work with and stuff. I really just want to help in any tiny way to make someone’s day a little easier. I try to make people smile.

And yet simultaneously people always find a way to butt into my life. To make me uncertain and doubt myself and mess with my head. To invade my privacy and meddle in any kind of relationships I have. How are we supposed to combat this when wanting to stay within our morals?

On another note, how do you differentiate people just messing around and accidentally harming your mental health, or people purposefully trying to worsen it?

Is this normal in the human experience? Have I just gotten unlucky with shit people around me?
It/they could all seem worse than it is. Yet this all happens again and again and again.