Th' expense of spirit in a waste of shame
Is lust in action; and till action, lust
Is perjur'd, murd'rous, 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 prov'd, a very woe;
Before, a joy propos'd; 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/sonnet-129/
