When you are old and grey and full of sleep,
And nodding by the fire, take down this book,
This poem opens, strikingly, with a command and a direct second-person address. Thus, the reader feels immediately implicated in the poem, not merely as a witness but as an active participant. This is made even more true given the specific task the speaker details: that is, to read "this book," the book that contains the very poem the reader is currently reading. In other words, by virtue of simply reading this command, the reader is already fulfilling it, since they cannot absorb the instruction to read the poem without in fact reading the poem containing the instruction. This means that the reader is strongly identified with the poem's addressee from these first lines, increasing the emotional resonance of the work.
But one man loved the pilgrim soul in you
The word "pilgrim" is a loaded, evocative one. Most literally, a pilgrim is a person who takes a trip to a religious or sacred site. The use of the word therefore suggests that the speaker's lover is devoted and soulful. However, a pilgrim can also be a person who explores or wanders, especially to a new, unexplored, or strange place. With this definition comes a new set of connotations: loneliness, independence, adventurousness, and bravery. By using this word, Yeats suggests that what the speaker most enjoys about the lover is her elusiveness. If she is constantly moving and changing, as "pilgrim" suggests, she is both difficult to maintain a relationship with, and nevertheless interesting and fascinating.
Murmur, a little sadly, how Love fled
And paced upon the mountains overhead
Though the second stanza suggests that it is the lover who cannot sit still or remain the same, the third stanza flips this dynamic. Here, the speaker suggests that it is in fact he who has disappeared and run away. The reasons for this disappearance are never given. However, what is clear is that, to an extent, the relationship roles have been reversed. Now it is the lover who sits at home reminiscing, and the speaker who is remembered as an elusive, unrestrainable figure.
