Krsna consciousness is not manufactured by us through mental speculation. It is prescribed in the Bhagavad-gita, which says that when we think in Krsna, chant in Krsna, live in Krsna, eat in Krsna, talk in Krsna, hope in Krsna, and sustain in Krsna, we return to Krsna, without any doubt. And this is the substance of Krsna consciousness.

(From "Science of Self-eralization" by Srila Prabhupada)