A crazy man that found a cup,
When all but dead of thirst,
Hardly dared to wet his mouth
Imagining, moon-accursed,
That another mouthful
And his beating heart would burst.
October last I found it too
But found it dry as bone,
And for that reason am I crazed
And my sleep is gone.

William Butler Yeats

http://www.poemhunter.com/poem/a-man-young-and-old-v-the-empty-cup/