" However, the references to loss in this stanza have become more specific, such as lost keys. Only in the fourth and fifth stanzas does the poet's personal emotion break into the form of the poem, and the tone become more personalized and confessional: "I lost my mother's watch. And look! my last, or next-to-last, of three loved houses went. The art of losing isn't hard to master." Against the generic repeated line of the first stanza, the first-person narration sounds as if the poet is trying to convince herself, rather than instruct the reader. Structurally, this sense of the pain of losing is intensified, as more irreplaceable thing are lost by the poet than a hour or keys, like watches and houses as the poem unfolds. The fifth stanza further personalizes and specifies the poet's loss and essentially raises the stakes of what has been lost in the past, as the poet admits she has lost kingdoms and entire realms. Then...

The poet turns from addressing an anonymous reader presumably seeking to learn how to lose, as the poet did at the beginning of the poem, to the lover the poet has lost.
The sense of emotion breaking through the verse form is confirmed by the breaking of the villanelle form itself. While a villanelle is supposed to end with a repetition of the two, ending refrains that have alternated through the poem, the poet herself intrudes, forces herself to "Write it" -- to write that losing her lover is not a disaster, even though it evidently feels like one. The poet still denies her emotion, but this denial, over the course of the poem has become harder and harder for her to believe, and her inability to continue or believe in the form of the villanelle parallels her inability to convince herself of the insignificance of her loss.