"My dear Lord, while traveling in this material world through different species of life, a living entity may progress toward liberation. But if, by chance, he comes in contact with a pure devotee, he becomes actually liberated from the clutches of material energy and becomes a devotee of Yourself, the Personality of Godhead."
When a conditioned soul becomes a devotee of Kṛṣṇa, the Lord, by His causeless mercy, trains him in two ways: He trains him from without through the spiritual master, and He trains him from within through the Supersoul. As stated in Śrīmad-Bhāgavatam (11.29.6): "My dear Lord, even if someone attains a life as long as Brahmā's, he would still be unable to express his gratitude for the benefits derived from remembering You. Out of Your causeless mercy You drive away all inauspicious conditions, expressing Yourself from outside as the spiritual master and from inside as the Supersoul."
Somehow or other if one gets in touch with a pure devotee and thus develops a desire to render devotional service to Kṛṣṇa, he gradually rises to the platform of love of Godhead and is thus freed from the clutches of material energy. This is also explained in Śrīmad-Bhāgavatam (11.20.8) where the Lord Himself says: "For one who is attracted by My activities out of his own accord—being neither lured nor repelled by material activities—the path of devotional service leading to the perfection of love of God becomes possible." However, it is not possible to achieve the stage of perfection without the favor of a pure devotee, or a mahātmā, a great soul. Without the mercy of a great soul, one cannot even be liberated from the material clutches, and what to speak of rising to the platform of love of Godhead.