TH' expense of Spirit in a waste of shame
Is lust in action; and till action, lust
Is perjured, murderous, bloody, full of blame,
Savage, extreme, rude, cruel, not to trust;
Enjoy'd no sooner but despised straight;
Past reason hunted; and, no sooner had,
Past reason hated, as a swallow'd bait
On purpose laid to make the taker mad:
Mad in pursuit, and in possession so;
Had, having, and in quest to have, extreme;
A bliss in proof, and proved, a very woe;
Before, a joy proposed; behind, a dream.
   All this the world well knows; yet none knows well
   To shun the heaven that leads men to this hell.

William Shakespeare

http://www.poemhunter.com/poem/sonnets-xix/