The speaker is caught off guard by the finality of loss: the sudden realization that someone beloved is truly gone, and that she must go on living alone. That knowledge feels too enormous and empty to accept, and the direct address—“My dear, my own”—makes the grief feel intimate, almost whispered.
The second half reflects on how time usually softens pain. The “merciful slow years” wound and take things away, but they also allow some healing. Yet one sharp moment, “one great throb,” can shatter that recovery and bring back the old sorrow as intensely as ever. The mood is quiet, tender, and heavy with longing, as if the speaker is speaking to someone who can no longer hear her.