[McClatchy is discussing the last stanza.]
… The loss of love here is not over and thereby mastered, but threatened: a possibility brooded upon, or an act being endured. How Bishop dramatizes the threatened loss is uncanny. "I shan’t have lied," she claims. Under such intense emotional pressure she shifts to the decorous "shan’t," as if the better to distance and control her response to this loss, the newest and last. And again, my mind’s ear often substitutes "died" for "lied." In self-defense, lying makes a moral issue out of the heart’s existential dilemma; a way of speaking is a habit of being. The real moral force of her stanza comes – and this is true in many other Bishop poems – from her adverbs:even losing you; not too hard to master. These shades of emphasis are so carefully composed, so lightly sketched in, that their true dramatic power is missed by some readers.
And then that theatrical last line – how severely, how knowingly and helplessly qualified! It reminds me of that extraordinary line in "At the Fishhouses," at three removes from itself: "It is like what we imagine knowledge to be." The line her begins with a qualification ("though"), goes on to a suggestion rather than the assertion we might expect of a last line ("it may look"), then to a comparison that’s doubled, stuttering ("like … like"), interrupted by a parenthetical injunction that is at once confession and compulsion, so that when "disaster" finally comes it sounds with a shocking finality.
The whole stanza is in danger of breaking apart, and breaking down. In this last line the poet’s voice literally cracks. The villanelle – that strictest and most intractable of verse forms – can barely control the grief, yet helps the poet keep her balance. …
From J. D. McClatchy, "Elizabeth Bishop: Some Notes on ‘One Art,’" in White Paper: On Contemporary American Poetry (New York: Columbia University Press, 1989), 145.