How has all the knowledge in the world been gained but by the concentration of the powers of the mind? The world is ready to give up its secrets if we only know how to knock, how to give it the necessary blow. The strength and force of the blow come through concentration. There is no limit to the power of the human mind. The more concentrated it is, the more power is brought to bear on one point; that is the secret.

The Complete Works of the Swami Vivekananda (ed. 1915)