The bestial civilization of eating, sleeping, fearing, and sense-gratifying has misled modern man into forgetting how powerful a soul he has. … The soul is a spiritual spark many, many times more illuminating, dazzling, and powerful than the sun, moon, or electricity. Human life is spoiled when man does not realize his real identity with his soul.

His Divine Grace A.C. Bhaktivedanta Swami Prabhupada
Caitanya-caritamrta, Adi-lila 5.22 , purport

For the soul there is neither birth nor death at any time. He has not come into being, does not come into being, and will not come into being. He is unborn, eternal, ever-existing, and primeval. He is not slain when the body is slain.

Lord Sri Krsna
Bhagavad-gita 2.20

With one-pointed attention, one should constantly hear about, glorify, remember, and worship the Personality of Godhead, who is the protector of the devotees.

Suta Gosvami
Srimad-Bhagavatam 1.2.14

No one can understand Krsna as He is by the blunt material senses. But He reveals Himself to the devotees, being pleased with them for their transcendental loving service unto Him.

Srila Rupa Gosvami
Bhakti-rasamrta-sindhu 1.2.234

"The living entities are fragmental parts of the supreme shelter, Krsna, but have fallen from Krsna's kingdom of spiritual pastimes. Because of forgetting the Supreme Lord, they become prone to sinful life and turn their attention to dangerous material objects, which fill them with constant fear. If one desires to subdue the mind, which is constantly engaged in the duality of mental concoction, one must take to the devotional service of Lord Krsna."

Srila Bhaktisiddhanta Sarasvati Thakura
Commentary on Srimad-Bhagavatam 11.2.38

Devotion, direct experience of the Supreme Lord, and detachment from other things these three occur simultaneously for one who has taken shelter of the Supreme Personality of Godhead, in the same way as pleasure, nourishment, and relief from hunger come simultaneously and increasingly, with each bite, for a person engaged in eating.

Sri Kavi Rsi
Srimad-Bhagavatam 11.2.42

Do not discriminate in your heart between enemies and friends; make your mind equipoised toward everyone. Except for the uncontrolled and misguided mind, there is no enemy within this world. When one sees everyone on the platform of equality, one then comes to the position of worshiping the Lord perfectly.

Prahlada Maharaja
Srimad-Bhagavatam 7.8.9