In the first place, it is usually harmful for a man to set up as a Guru before he has attained realization himself.
It impedes his further progress on the path by turning his energy outward to the guidance of others when it should still be turned inward to his own sadhana. If not impossible for such a person to make further progress, it is at least much more difficult. Not only that, but there is danger of his latent egoism being revived, bringing him to a worse state than he was in before.
If the ego still exists, it may lie low for a while, facilitating the flow of Grace , and then rise up and turn this to its own service, poisoning it in the process.
Moreover, there is the danger of hypocrisy and arrogance. So sweet is adulation to the ego that he is likely to allow his disciples to treat him as a realized man when he is not, which is hypocrisy. Or he will become arrogant or overbearing, craving flattery, refusing to listen to criticism, shouting down arguments.
It is foolish to invite such dangers, which few can withstand.
From For Those with Little Dust by Arthur Osborne, long-time editor of Ramana Maharshi | 