I'm really glad Rihanna chose to write about her experience with a really bad relationship. I can relate, as can a good majority of the world. The song is just about her coming to terms with the fact that it's just plain stupid to stay with this guy and keep giving him more chances. He is obviously not a good guy and not the right guy for her. She is basically saying, I've done some dumb things, I've let you take advantage of me all this time, but I'm not stupid enough to take you back again, I'm done.
I'm really glad Rihanna chose to write about her experience with a really bad relationship. I can relate, as can a good majority of the world. The song is just about her coming to terms with the fact that it's just plain stupid to stay with this guy and keep giving him more chances. He is obviously not a good guy and not the right guy for her. She is basically saying, I've done some dumb things, I've let you take advantage of me all this time, but I'm not stupid enough to take you back again, I'm done.