Hearts are often symbolic of love, and a heart with a dagger through it is often seen as a sign of heartbreak or betrayal, especially in tattoo iconography. The fact that the “dagger” (Line 1) is “held in the fist / of a shuddering heart” (Line 1) shows that as much as the heart “shudder[s]” (Line 1), it still grips the implement wounding it. Symbolically, this suggests the man holds onto that which wounded him. He can’t let go of the betrayal, so it becomes a “bruise” (Line 3) where “vanity once punched him hard” (Line 5). This is echoed in the last line, where the speaker describes the man with “his heart gone soft and blue” (Line 15). Here, the “heart” (Line 15) could also literally refer back to the faded tattoo, which is “soft and blue” (Line 15) like a “bruise” (Line 3), or the “heart” (Line 15) of the man, which is “soft and blue” (Line 15) with emotional damage. The heart is both a real description of a design on the man’s skin and a symbol of his inner life.