This song has a similar lyrical content to that of Usher’s major hit “Confessions” and its sequel. Usher sat down with EW to explain it’s concept a little bit more:
It’s about a guy who makes a mistake [infidelity] and has an understanding with his woman that it’s okay — but she really didn’t forgive him. And trying to get her to get over it is like moving a mountain.
https://www.youtube.com/watch?v=nQr-HmfXZ-Q