Jessea L. Vaughan's poem is a long list of things that never came to be: a game unplayed, a book unread, a house built but never lived in. Almost every line uses the same trick, attaching "un-" to an ordinary word, so that absence becomes the subject. At first the items are small and almost casual, like a skipped dinner or a day spent in bed. That gentle start makes the turn near the end land harder.
In the final lines the poem reveals what the list was building toward: a person "we all un-met," whose story stays untold and whose dreams are unknowable. The speaker seems to be mourning someone whose life never fully happened, though the poem doesn't say how or why. The mood is quiet, wistful and sad, with a note of regret. The repeated "un-" words feel like a slow drip of loss, and the closing echo of the title, "a promise unfulfilled," leaves the reader sitting with everything that might have been.