Constantine P. Cavafy - He vows

Every so often he vows to start a better life.
But when night comes with her own counsels,
with her compromises, and with her promises;
but when night comes with her own power
of the body that wants and demands, he returns,
forlorn, to the same fatal joy.

Constantine P. Cavafy

http://www.poemhunter.com/poem/he-vows/