“Being Irish, he had an abiding sense of tragedy, which sustained him through temporary periods of joy.” WILLIAM BUTLER YEATS, Irish Poet and Dramatist (1865-1939)
Painting: “Blue William Butler Yates,” acrylic on canvas by Frank Cullen. Find prints of the portrait at fineartamerica.com.
Silver Birch Press 
Please let me know if you find any evidence that Yeats actually said or wrote this, where and when. Otherwise, this attribution seems to be a myth fabricated sometime in the early 1990s.
Thanks for pointing this out. I am torn between deleting this post and leaving it with your comment. Perhaps leaving it will start a discussion. Thanks again.