Dave Bonta's short poem catches a very ordinary moment, dinner bubbling on the stove, and lets something unsettling slip in. The speaker suddenly feels old, and the feeling seems to arrive from nowhere. They call it "a miracle," which is an odd word to use. It suggests astonishment more than sadness, as if the speaker is watching the change happen to someone else.
The image of the "changeling" is the heart of it. In folklore, a changeling is a creature left in place of a stolen child. The speaker feels like that: the same person on the outside, yet replaced by someone unfamiliar. Aging has gone "beyond all imitation of a face," so even the face no longer looks like a copy of who they were. The title, "Memento mori" (Latin for "remember that you must die"), adds a quiet note of mortality. The mood is calm but eerie, a small private shock in the middle of a domestic scene.