English idiom meaning to accept the consequences of one's actions. There is uncertainty as to its origin, because in the phrase's earlier usage (1850s) it meant to have courage in general, not just when facing the consequences of something. It is likely derived from either theatre or military.

When a nervous theatrical performer would go on stage they would not only be facing the audience, but the orchestra as well.
When an English soldier was being dismissed from his regiment it was sometimes the practice for the band to play "Rogue's March."

When I walked to my neighbor's door I thought, "It is my fault for flooding her basement. Now I have to face the music; I hope she isn't too mad."