In every step there is perplexity, and therefore it behooves one to approach a bona fide spiritual master who can give one proper guidance for executing the purpose of life. All Vedic literatures advise us to approach a bona fide spiritual master to get free from the perplexities of life, which happen without our desire.
(Bhagavad-gita Chapter 2, Purport of Text 7)

guidance of a spiritual master

Even Krishna, the Supreme Personality of Godhead, accepted Sandipani Muni as His teacher or master. Although Sri Chaitanya Mahaprabhu is an incarnation of Krishna, He accepted Ishvara Puri as His Guru. They do not require Guru, but just to keep pace with the official program, even God personally accepted spiritual master. So this is essential. Acharyopasanam. 
(Bhagavad-gita Lecture 13.8.12, Bombay, October 2, 1973)

The Vedic wisdom therefore advises that in order to solve the perplexities of life and to understand the science of the solution, one must approach a spiritual master who is in the Disciplic Succession (Guru Parampara).
(Bhagavad-gita Chapter 2, Purport of Text 7)