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,
Enjoyed no sooner but despisèd straight,
Past reason hunted, and no sooner had
Past reason hated as a swallowed 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/sonnet-129-th-expense-of-spirit-in-a-waste-of-sh/