Ishvara (God) is guru of gurus. He removes the veil of ignorance and blesses the ignorant jiva (soul). The aspirant should regard his immediate guru - in the physical form - as an incarnation of that Guru of all gurus. He should have equal devotion to him. Guru in physical form is the main source and embodiment of all good and happiness that accrues to the disciple.
The disciple should realise the supreme necessity for obeying the guru's commands and behests. He should keep his faith in the guru unsullied and staunch. Lay bare to your guru the secrets of your heart. The more you do so, the greater the sympathy. And this means an accession of strength to you in the struggle against sin and temptation. A spiritual teacher actually transmits his spiritual power to his disciple.
A certain spiritual vibration of the satguru is actually transferred to the mind of the disciple. Sri Ramakrishna Paramahamsa actually transmitted his spiritual power to Swami Vivekananda. Lord Jesus did the same to his disciples. This is the master's touch.
It is he who transmutes the little jiva (soul) into great Brahman, infinite. It is he who overhauls the old, wrong, vicious nature (samskaras) of aspirants and awakens them to the attainment of knowledge of the self. It is he who uplifts the jivas from the quagmire of body and samsara (worldly life), who removes the veil of avidya (ignorance), all doubts, fears, etc. It is he who awakens the kundalini and opens the eye of inner intuition.
Never look into the defects of the guru. Deify the guru. Guru, Ishvara, Brahman, Om, truth, are all one. Strictly obey the guru and carry out his orders. You must think that underneath the name and the form of the guru there is the all-pervading, pure consciousness. In course of time the physical form will vanish and you will realise your own self, the pure Brahmic consciousness that lies at the back of the physical form of your guru.
Once you have taken a man as your guru you should never change even if you get a man with greater siddhis (development). Then only you will have strong faith. And through this strong faith you will realise God in the guru.