Yeats speaks to the woman he loves by imagining her already old: when you are old and grey, by the fire, take down this book, read it slowly, and remember the soft look your eyes once had. Many loved your beauty, with love false or true; but one alone loved «the pilgrim soul» in you, and loved the sorrows of your changing face.
The poem — addressed to Maud Gonne, Yeats's great unrequited love — sets apart those who wanted the beauty from the one who wanted the person. In the last stanza Love, now lost, flees to the mountains and hides his face among the stars: the sweet, sad warning of one who knows that his was the only love that would last.