Sounds to me the guy here is watching his girl change after the honeymoon of the relationship is over. All the promises she said are not being fulfilled while he comes through on all his. He wonders now if he made a mistake loving her as he is paying a hard emotional price in the form of being jaded by her. As he enters what he feels is the twilight of his resolve to endure, he confronts her on all the promises she failed to uphold, with the most meaningful promise being that she would die for him, in essence do anything for him. How everything will end is left for the listener though there is a heavy lean toward the ending of it is hinted at. This could easily be vis versa with a girl instead of a guy but to me the meaning remains the same.