The spiritual master and Krishna are two parallel lines. The train, on two tracks, moves forward. The spiritual master and Krishna are like these two tracks, they must be served simultaneously. Krishna helps one to find bona fide spiritual master and bona fide spiritula Master helps one to understand Krishna. If one does not get bona fide spiritual master, then how he can ever understand Krishna? You cannot serve Krishna without spiritual master, or serve just spiritual master without serving Krishna. They must be served simultaneously. — Letter to Mahapurusha, 12th Feb, 1968.
If we take shelter of the lotus feet of the spiritual master, we can become free from illusion, fear and distress. If we wholeheartedly beg for his mercy without any deceit then the spiritual master bestows all auspiciousness upon us.
When you come before spiritual master, be prepared to get chastised. Spiritual Master's business is to do that. Shisya means who is ready is accept 'sashan' or ready dor getting chastisement.
Out of many millions of wandering living entities, one who is very fortunate gets an opportunity to associate with a bonafide spiritual master by the grace of Krishna. By the mercy of both Krishna and the spiritual masters, such a person receives the seed of the creeper of devotional service.
It is dangerous for a spiritual master to accept almost any aspirant. Although it is an aspect of mercy, it is dangerous. The danger also depends on the spiritual potency of the particular guru. Without sufficient potency, a few offensive or faithless disciples can lead to the guru’s fall.