William Butler Yeats (13 June 1865 – 28 January 1939 / County Dublin / Ireland)

His friends have betrayed him and his wife was his only escape. i think

one of the most beautiful love poems I've ever read

Those familiar with Yeats biography know that this poem refers to Maud Gonne. In 1889, Yeats met Gonne, then a 23-year-old heiress and ardent Nationalist. Gonne was eighteen months younger than Yeats and later claimed she met the poet as a 'paint-stained art student.' Gonne had admired 'The Isle of Statues' and sought out his acquaintance. Yeats developed an obsessive infatuation with her beauty and outspoken manner, and she was to have a significant and lasting effect on his poetry and his life thereafter. In later years he admitted 'it seems to me that she [Gonne] brought into my life those days—for as yet I saw only what lay upon the surface—the middle of the tint, a sound as of a Burmese gong, an over-powering tumult that had yet many pleasant secondary notes.' Yeats' love initially remained unrequited, in part due to his reluctance to participate in her nationalist activism. His only other love affair during this period was with Olivia Shakespear, whom he had first met in 1896, and parted with one year later. In 1891, he visited Gonne in Ireland and proposed marriage, but was rejected. He later admitted that from that point 'the troubling of my life began'. Yeats proposed to Gonne three more times: in 1899,1900 and 1901. She refused each proposal, and in 1903, to his horror, married the Irish nationalist Major John MacBride.

It's obvious that Yeats is playing with punctuation. Add a comma after 'OTHERS' and 'VOW' and the true meaning becomes visible:
~
OTHERS, because you did not keep That deep-sworn vow,
have been friends of mine;
~
Yeats is saying that he has had other lovers, only because of his wife's act of adultery, breaking their wedding vows. And yet, because of his deep love for her, he is constantly reminded of her throughout his life.

i don't think this is about his 'unfaithful' wife.....
this is more likely a
bout himself....
and that durng times he thought of going with other women...he can think about the vow he promised to his wife...the vow probably that he recited during their wedding ceremony...its presented here....

Or when I grow excited with wine,
Suddenly I meet your face.

This is one of my 108 favorite poems

Despite the note below this lovely poem, it is about neither sleep, death, nor friend! Read it. It is like all truly great poems in that it is not entirely explainable, but I can say that it is about a depth of love and loss that cannot be assuaged. Yeats has had lovers since, but at all unguarded moments, he remembers his only great love-very likely his wife (the deep-sworn vow) who was unfaithful to him.