The speaker is talking directly to their own heart, and the tone is a mix of hurt, frustration, and confusion. They can't understand why someone who treats them badly, a "jerk" who doesn't respect their feelings and "throws them around," holds so much of their love. The most painful detail is that this same person has "everything I am," which suggests the speaker has given far more of themselves than they got back.
The repeated "Why" makes the poem feel like a question the speaker has asked many times without an answer. Near the end, the speaker shifts from blaming the other person to blaming the heart itself: "I didn't choose him, / But you did." It reads as someone who feels their emotions are out of their control, caught between what their head knows and what their heart wants. The poem stops abruptly on "You chose him," leaving a raw, unresolved mood of helplessness and quiet resentment.