In just a few lines, this short poem sets a grey, damp morning beside bad news: the speaker's illness has come back. The title, "Recurrence," names the dread of something you hoped was over returning.
The surprise is in the last line. The speaker doesn't complain or panic. Instead they "drink / to my physician," raising a glass to the doctor. The line break after "I drink" makes the gesture hang for a second before we learn who the toast is for. The tone is hard to pin down. It could be dark humor, a way of facing bad news with a shrug. It could be real gratitude toward the person who will help. It could also be a hint of resignation, a drink to dull the shock.
The "misting morning" fits all of these. It feels soft, blurry and uncertain, like the speaker's future. The mood is quiet and wry, with fear underneath, and the speaker seems to meet that fear with dry composure.