Sam M's poem is about the loneliness of feeling cut off from everyone around you, even when you're surrounded by people. The speaker watches others smile and wonders which of those smiles are fake, and whether anyone could understand the "darkness seeping" inside. From there the poem moves to numbness. At first it seems like relief, a way to stop the pain, but then people miss the pain because at least it felt like something. The numbness frightens them, and the poem insists there's no going back from it.
The speaker slips between "they" and "you," as if describing others while really describing themselves. The mood is bleak and heavy, with short, flat lines that mimic the emptiness being described. The ending is the darkest turn: the poem suggests giving up and dying without saying goodbye. The last question, asking whether people who caused this pain deserve a goodbye, mixes anger with hurt. It reads as a painful cry to be noticed.