"Desire is the cause of action, because it urges one to action.
"Those who have obtained the fruit of all their desires are free from desires; therefore they are established in the Self and cannot feel any urge to action. When one cherishes the desire for the Self, all one's desires are fulfilled. The Self is Brahman.... the knower of Brahman attains the Supreme Goal. Therefore when, after cessation of ignorance, a person dwells in the Self, he realizes the Supreme Goal. For the scriptures say: 'When a man [knows the Self] he has then obtained fearlessness.' 'He... attains the Self which consists of bliss.'"
-Adi Shankaracharya (introduction to the Taittiriya Upanishad)