Why do narcissist find one thing and make up some shit in their head

It's very painful when they sit there, and they make up stuff right in front of you, then they believe it and take it to a whole other level. And nothing you say or do will change how they are thinking. If they want you to feel bad and hate yourself, they will make you feel that way. If you start crying, they say your tears don't mean anything, and you're faking. They don't want you to tell your truth they want you to say what their truth is, and that's all that matters. It's so confusing. Why do this. What is the point? How could you like seeing someone in pain. You try to stone (Grey)wall them, but sometimes it's hard because you want to stick up for yourself. You can't accept the type of disrespect, but it only gets more disrespect switch for you to love one back to you and