The speaker is struggling to say who they are right now. They begin by admitting they are "just what I told you / and not," as if their own account of themselves was only half true. Something has gone missing, and they call it "the Sympathy," capitalized, almost like a person who has wandered off. Whatever kindness or feeling they once had to give, it no longer seems theirs to offer, at least for now.
What has taken its place is weight. The wordplay on "weight" and "wait" is the poem's sharpest moment: the heaviness arrived quickly, while the waiting, the hope that things would pass, was slow to leave, or only tried to. The closing image of sparrows hopping in and out brings in the poem's last comparison. Their visits are uncertain, wanting but not daring, then gone. The broken, hesitant lines mimic that nervous movement. The mood is tired, numb, and quietly sad, with a little honesty in how plainly the speaker admits their own inconsistency.