Mack's "miss" is a farewell letter written by someone who left without ever saying goodbye. The speaker admits to being a coward, frantic and naive, and says plainly that they miss the person they left behind. That person was "my yellow," a bright presence who made ordinary days feel idyllic. The speaker insists the bond wasn't romantic, but sweet and quaint, until something, "the truth," forced them to go.
The mood is tender and regretful, with a sense of guilt running underneath. The speaker blames fear for their silence and admits their words were "insubstantial" next to what they actually thought. The sunshine imagery, with light, glimmer and hope in the "mid of night," shows how much this person mattered. Yet the line "i love you for trying / but try with all your might, / i'm gone" is final. The signature, "the one who never said goodbye," makes the poem itself the goodbye that was always owed, even if it comes late.