Every relationship must come to an end eventually, whether through death or breakup. And while most people hope to stay together until death do them part, or there's a mature and mutually agreed upon split, a lot of relationships end in painful, sometimes sudden break-ups.
When you've been together awhile, it's natural to get used to your partner's flaws and all of the complex relationship dynamics. While this can be healthy to a certain extent, it can also make it harder to fully see how toxic things can get. So, sometimes a very obvious "f*ck this" moment is what's needed in order to leave a bad relationship.
I was 17, so its a while ago. My boyfriend was 19. I told him I wanted to break up because he was all over me. Had no friends, just me. If I was talking to his sister, he got jealous. I realized he was toxic and I realized I couldn't help him.