Our advancement in Krishna Consciousness is made possible in two ways, by knowledge and renunciation, jnana and tyaga or tapasya. The more we become renounced from this material world, the more we advance in Krishna Consciousness. But we are only able to make such sacrifices and perform tapasya if we have got knowledge. So first thing is to become knowledgeable in Krishna Consciousness, then the tapasya or voluntary life of austerity will result automatically. So I am requesting all of my students to read my books very seriously every day without fail. In this way, if your mind becomes absorbed at least one or two hours daily in the transcendental subject matter of Srimad-Bhagavatam, Bhagavad-gita, and other books then very easily you will make your advancement in Krishna Consciousness.
(From Srila Prabhupada's letter to Bhargava — Los Angeles. 13 June, 1972)