One should act according to the order of Krsna. This is a very important point. That order of Krsna comes through disciplic succession from the bona fide spiritual master. Therefore the spiritual master's order should be taken as the prime duty of life. If one gets a bona fide spiritual master and acts according to his direction, then one's perfection of life in Krsna consciousness is guaranteed.
His Divine Grace A.C. Bhaktivedanta Swami Prabhupada
Bhagavad-gita As It Is 18.57, Purport
Pure devotional love of God is unattainable without great faith, without intense eagerness to relish the nectarean pastimes of the Supreme Lord, and without a deep understanding of the esoteric truths of the scriptures.
Srila Bhaktivinoda Thakura
Sri Sanmodana Bhasyam (commentary of Lord Caitanya's Sri Siksastaka)
Pure love for Krsna is eternally established in the hearts of the living entities. It is not something to be gained from another source. When the heart is purified by hearing and chanting [about Krsna], the living entity naturally awakens.
Sri Caitanya Mahaprabhu
Sri Caitanya-caritamrta, Madhya 22.107
Both animals and men share the activities of eating, sleeping, mating, and defending. But the special property of the humans is that they are able to engage in spiritual life. Therefore, without spiritual life, humans are on the level of animals.
Who can be worthy of the name of the Supreme Lord but the Personality of Godhead Sri Krsna? Brahmaji collected the water emanating from the nails of His feet in order to award it to Lord Siva as a worshipful welcome. This very water [the Ganges] is purifying the whole universe, including Lord Siva.
Sri Suta Gosvami
The holy name of Krsna is the highest benediction. It is sweeter than the sweetest honey, and it is the fruit of transcendental knowledge of the tree of the entire Vedic scriptures.
Quoted in Hari-bhakti-vilasa (11.234)
The word krs is the attractive feature of the Lord's existence, and na means spiritual pleasure. Krs added to na becomes Krsna, which indicates the Absolute Truth.
Mahabharata, Udyoga Parva 71.4