The speaker confronts a man who abuses his girlfriend, opening with a sharp, sarcastic question: does hurting her make him feel like a man? The poem is aimed straight at him, and the tone is angry and accusing, though it is also full of sorrow for the woman.
She is shown as devoted. She was his "biggest fan," and she is willing to give up her own comfort so that he can have his. Yet she wakes up with new bruises and covers for him, saying he "wasn't around." That protectiveness is what makes the poem so painful. The more she shields him, the more trapped she seems.
The ending suggests the damage goes deeper than the physical. His violence has worn down her ability to love, so that she can hardly love him now, and she is allowed to love only a few people. The mood is heavy and bitter, built on frustration at the abuse and at how much it takes from her.