Faith in Guru and Surrender to Kṛṣṇa
77
manuṣyāṇām sahasreṣu kaścid yatati siddhaye yatatām api siddhānām kaścin mām vetti tattvataḥ
“Out of many thousands among men, one may endeavor for perfection, and of those who have achieved perfection, hardly one knows Me in truth.” (Bg. 7.3)
Thus out of many perfected spiritualists, one man may know what Kṛṣṇa actually is. As this verse indicates, the subject matter of Kṛṣṇa is not so easy but is very difficult. Yet  Bhagavad-gītā  also indicates that it is easy.
bhaktyā mām abhijānāti yāvān yaś cāsmi tattvataḥ tato mām tattvato jñātvā viśate tad-anantaram
“One can understand the Supreme Personality as He is only by devotional service. And when one is in full consciousness of the Supreme Lord by such devotion, he can enter into the kingdom of God.” (Bg. 18.55)
If we accept the process of devotional service, we can understand Kṛṣṇa very easily. Through it we can understand the science of Kṛṣṇa perfectly and become eligible for entering into the spiritual kingdom. If, as  Bhagavad-gītā  says, after many births we have to eventually surrender to Kṛṣṇa, why not surrender to Him immediately? Why wait for many, many births? If surrender is the end of perfection, why not accept perfection immediately? Of course the answer is that people are generally doubtful.