Kjhawk's short poem is about love and loss, and it turns on its last line. For most of the poem the speaker sounds warm and certain. Your smile makes me smile, your eyes say so much, and each time the speaker adds "I knew it would" or "I knew they could," as if this closeness was always meant to happen. Even the hugs feel familiar before they ever took place, which suggests a bond that felt almost fated.
Then the final line changes everything. The speaker says they missed this person before they met them, and now they miss them because they are gone. The poem doesn't say how or why the person left, so we're left with the feeling alone. The mood begins tender and gentle, then settles into quiet sadness. The repeated word "miss" links longing before the relationship to grief after it, as though this person filled a space the speaker had always felt was empty, and now it is empty again.