A scientist sets out to conquer nature through knowledge - external nature, external knowledge. By these means he may split the atom and achieve external power. A yogi sets out to explore his own internal nature, to penetrate the atom (atma) of being. He does not gain dominion over wide lands and restless seas, but over his own recalcitrant flesh and febrile mind.
B.K.S. IyengarHe who has learnt to control his tongue has attained self-control in a great measure. When such a person speaks he will be heard with respect and attention. His words will be remembered, for they will be good and true. When one who is established in truth prays with a pure heart, then things he really needs come to him when they are really needed: he does not have to run after them. The man firmly established in truth gets the fruit of his actions without apparently doing anything. God, the source of all truth, supplies his needs and looks after his welfare.
B.K.S. Iyengar