Yeats was in love with Maud Gonne for virtually his whole life--she rejected his marriage proposals three times with the last proposal made in 1916. This was the year before he married his wife. He may have had Maud in mind in A Deep-Sworn Vow in spite of the fact she never made a vow. The following is one of the early "Maud" poems. It was written while he was young.

When You Are Old

When you are old and grey and full of sleep,
And nodding by the fire, take down this book,
And slowly read, and dream of the soft look
Your eyes had once, and of their shadows deep;

How many loved your moments of glad grace,
And loved your beauty with love false or true,
But one man loved the pilgrim soul in you,
And loved the sorrows of your changing face;

And bending down beside the glowing bars,
Murmur, a little sadly, how Love fled
And paced upon the mountains overhead
And hid his face amid a crowd of stars.

To be loved for my "pilgrim soul" would be wonderful.

Chuck