Sri Nityananda caritamrita, Hare Krishna book

That without the mercy of Lord Nityananda, no one can achieve Sri Radha and Krishna. The ultimate
goal of life is the achievement of Krishna-Prema. This is possible only by the mercy of sadhu-guru. Sri
Nityananda Prabhu is the sum total of all gurus (samashti-guru). He is guru-tattva. All individual gurus
(vyashti) are representations of Sri Nityananda. Srila Bhaktisiddhanta Sarasvati Thakura writes in the
Harmonist magazine about the manifestation of guru in the form of Sri Nityananda:
The guru is the embodiment of the manifestation of the Divinity to the pure receptive spiritual essence
of the disciple. Nityananda is the primary manifesting constituent of the Divinity. Nityananda alone
possesses the distinctive function of the guru. In Nityananda, the function is embodied. Nityananda is
the servant-God.