Me, being an ovethinker

Hello everyone. Just want to share some stories about myself. This is me, an overthinker. I'm always thinking the things that may or may not happen. But mostly i always thought all the negatives. Insane, right? Sometimes, it is just a simple scenario, but in my mind, I'm making it worse, to the point that I'm already hurting myself emotionally. Although, my imaginations didn't happen, I already hurt myself. For me, Im just thinking those things because I think I'm just preparing myself from the pain. That if they hurt me, I'll just say "okay" since I already predicted that. But, I realize that, the one who makes me sad is me. Me when I am overthinking. A simple problem, but I'm making it worse. But I dont know how to change myself. Can you give me an advice? Please?