There are two gurus - one internal and the other external. The internal Guru is Krishna Himself seated in everyone's heart, and the external Guru is the Spiritual Master. So a sincere devotee is helped both externally and internally. To the sincere devotee the internal Guru Krishna dictates, but the thing has to be conformed by the external Guru then it is all right.
Letter to Kancanbala dasi, 14 January, 1968