Regarding the eternal relationship that exists between yourself and your spiritual master, that eternal relationship is based upon the eternal instructions I am giving to you, aimed at purifying your heart. There are many details yet to be given, but they cannot be given until the heart is clean enough to receive them. Therefore, the most important instruction of the spiritual master is to chant Hare Krishna offenselessly. (Collected Letters to My Disciples, Vol 3, Pg 95 last Paragraph)