A person who has attained the stage of attraction for Kṛṣṇa and who is not freed from the material impasse, but who has qualified himself to enter into the kingdom of God, is called sādhaka. Sādhaka means one who is cultivating devotion in Kṛṣṇa consciousness. The description of such a devotee is found in the Eleventh Canto, 2nd Chapter, 45th verse, of Śrīmad-Bhāgavatam. It is said there that a person who has unflinching faith in and love for the Personality of Godhead, who is in friendship with devotees of Kṛṣṇa, and who is very merciful to the ignorant, raising them to the standard of devotional service, and who is uninterested in nondevotees, is considered to be situated in the position of cultivating devotional service.
When one is found shedding tears by hearing of the pastimes of the Lord, it is to be understood that the blazing fire of material existence will be extinguished by such watering. When there is shivering of the body and the hairs of the body stand up, it is to be understood that the devotee is nearing perfection. An example of a sādhaka cultivating devotional service is Bilvamaṅgala Thākur.
When a person is never tired of executing devotional service and is always engaged in Kṛṣṇa conscious activities, constantly relishing the transcendental mellows in relationship with Kṛṣṇa, the devotee is called perfect. This perfectional stage can be achieved in two ways: one may achieve this stage of perfection by gradual progress in devotional service, or one may become perfect by the causeless mercy of Kṛṣṇa, even though he has not executed all the details of devotional service. There is the following nice statement in the Third Canto, 15th Chapter, 25th verse, of Śrīmad-Bhāgavatam describing a devotee who achieves perfection by regularly executing devotional service: A person who is freed from the false egotism of material existence, or an advanced mystic, is eligible to enter into the kingdom of God known as Vaikuṇṭha. Such a mystic becomes so joyful by constant execution of the regulative principles of devotional service that he thereby achieves the special favor of the Supreme Lord. Yamarāja, the mighty superintendent of death, is afraid to go near such a devotee; so we can imagine the potency of advanced devotional service, especially when devotees sit together and engage in talking of the pastimes of the Supreme Personality of Godhead. Those devotees express their feelings in such a way that they automatically melt with ecstasy, and many transcendental symptoms become manifested in their bodies. Anyone desiring advancement in devotional service must follow in the footsteps of such devotees.