She's cheated on him, or in the videoclip of this song is the other way around. He cheats on him. Actually, the video is pretty good, depicts very well the relationship. What do you do when you know that they've cheated on you? that you've given everything of you and that person stumbles on your heart and crushes it every time he/she is with someone else, looks that other person in the eyes and is happy with them. I mean, what do feel then? maybe the only choice is this. That you're not the only one.