One should know, therefore, from the expert spiritual master, the advantages and disadvantages of discharging devotional service, just as Mahārāja Parīkṣit asked his spiritual master, Śrīla Śukadeva Gosvāmī. According to Bhakti-rasāmṛta-sindhu, the science of devotional service, one should not eat more than what he requires to maintain body and soul together. Vegetable diets and milk are sufficient for maintenance of the human body, and therefore one has no need to eat anything more to satisfy the palate.
(Srimad Bhagavatam-----2:8:21-----purport).

These different stages of gradual development increase love of God to the highest stage, and in the highest stage there are still more symptoms, such as affection, anger and attachment, gradually rising in exceptional cases to the mahā-bhāva stage, which is generally not possible for the living entities. All these were manifested by Lord Śrī Caitanya Mahāprabhu, the personification of love of God.
In the Bhakti-rasāmṛta-sindhu by Śrīla Rūpa Gosvāmī, the chief disciple of Lord Śrī Caitanya Mahāprabhu, these transcendental symptoms displayed by pure devotees like Uddhava are systematically described. We have written a summary study of Bhakti-rasāmṛta-sindhu entitled The Nectar of Devotion, and one may consult this book for more detailed information on the science of devotional service.
(Srimad Bhagavatam-----3:2:5-----purport).

That is the primary qualification for being one with the Lord. A person who is able to attain this transcendental qualification is called jīvan-mukta, or liberated, even though he is apparently in material conditions. This liberation is achieved by one who constantly engages in the transcendental loving service of the Lord. In Bhakti-rasāmṛta-sindhu (1.2.187) it is stated:
īhā yasya harer dāsye
karmaṇā manasā girā
nikhilāsv apy avasthāsu
jīvan-muktaḥ sa ucyate
"Anyone who, by his actions, mind and words, lives only for the transcendental loving service of the Lord, is certainly a liberated soul, even though he may appear to be in a condition of material existence." Uddhava was in such a transcendental position, and thus he was selected to be the factual representative of the Lord in His bodily absence from the vision of the world. Such a devotee of the Lord is never affected by material strength, intelligence or even renunciation. Such a devotee of the Lord can withstand all onslaughts of material nature, and therefore he is known as gosvāmī. Only such gosvāmīs can penetrate the mysteries of the Lord's transcendental loving relationships.
(Srimad Bhagavatam-----3:4:31-----purport).

The Lord fulfills the desires of everyone just as one desires. Pure devotees are interested in achieving the transcendental service of the Lord, which is nondifferent from Him. Therefore, the Lord is the only desire of the pure devotees, and devotional service is the only spotless process for achieving His favor. Śrīla Rūpa Gosvāmī says in his Bhakti-rasāmṛta-sindhu (1.1.11) that pure devotional service is jñāna-karmādy-anāvṛtam: (CC.2:19:167) pure devotional service is without any tinge of speculative knowledge and fruitive activities. Such devotional service is able to award the pure devotee the highest result, namely direct association with the Supreme Personality of Godhead, Lord Kṛṣṇa. According to the Gopāla-tāpanī Upaniṣad, the Lord showed one of the many thousands of petals of His lotus feet.
(Srimad Bhagavatam-----3:8:26-----purport).

In the Bhakti-rasāmṛta-sindhu it is said that a person whose only desire is to render transcendental loving service to the Lord is a free person in any condition of material existence. That service attitude is the svarūpa, or real form, of the living entity. Lord Śrī Caitanya Mahāprabhu, in the Caitanya-caritāmṛta, also confirms this statement by declaring that the real, spiritual form of the living entity is eternal servitorship to the Supreme Lord. The Māyāvāda school shudders at the thought of a service attitude in the living entity, not knowing that in the transcendental world the service of the Lord is based on transcendental love.
(Srimad Bhagavatam-----3:9:33-----purport).

Śrīla Rūpa Gosvāmī has given directions, in his Bhakti-rasāmṛta-sindhu, on how to accept a bona fide spiritual master and how to deal with him. First, the desiring candidate must find a bona fide spiritual master, and then he must very eagerly receive instructions from him and execute them. This is reciprocal service. A bona fide spiritual master or saintly person always desires to elevate a common man who comes to him. Because everyone is under the delusion of māyā and is forgetful of his prime duty, Kṛṣṇa consciousness, a saintly person always desires that everyone become a saintly person. It is the function of a saintly person to invoke Kṛṣṇa consciousness in every forgetful common man.
(Srimad Bhagavatam-----3:22:7-----purport).

Rūpa Gosvāmī explains very nicely in Bhakti-rasāmṛta-sindhu how this bhāva, or preliminary stage of love of God, is achieved. He states that one first of all has to become faithful (śraddhayānvitaḥ). Faith is attained by controlling the senses, either by yoga practice, following the rules and regulations and practicing the sitting postures, or by engaging directly in bhakti-yoga, as recommended in the previous verse. Of the nine different items of bhakti-yoga, the first and foremost is to chant and hear about the Lord. That is also mentioned here. Mat-kathā-śravaṇena ca. One may come to the standard of faithfulness by following the rules and regulations of the yoga system, and the same goal can be achieved simply by chanting and hearing about the transcendental activities of the Lord.
(Srimad Bhagavatam-----3:27:6-----purport).

The conditioned soul sees the flower for his own enjoyment, and the devotee sees the flower as an object to be used in the service of the Lord. In the same way, one can see the reflection of the Supreme Lord in one's own senses, mind and body—in everything. With that correct vision, one can engage everything in the service of the Lord. It is stated in the Bhakti-rasāmṛta-sindhu that one who has engaged everything—his vital energy, his wealth, his intelligence and his words—in the service of the Lord, or who desires to engage all these in the service of the Lord, no matter how he is situated, is to be considered a liberated soul, or satya-dṛk. Such a man has understood things as they are.
(Srimad Bhagavatam-----3:27:13-----purport).

The explanation by Rūpa Gosvāmī in the Bhakti-rasāmṛta-sindhu of how a person can be liberated even in this body is more elaborately explained in this verse. The living entity who has become satya-dṛk, who realizes his position in relationship with the Supreme Personality of Godhead, may remain apparently merged in the five elements of matter, the five material sense objects, the ten senses and the mind and intelligence, but still he is considered to be awake and to be freed from the reaction of false ego. Here the word līna is very significant. The Māyāvādī philosophers recommend merging in the impersonal effulgence of Brahman; that is their ultimate goal, or destination. That merging is also mentioned here. But in spite of merging, one can keep his individuality.
(Srimad Bhagavatam-----3:27:14-----purport).

This stage of life is explained by Rūpa Gosvāmī in his Bhakti-rasāmṛta-sindhu. A person whose mind is completely dovetailed with the desire of the Supreme Personality of Godhead, and who engages one hundred percent in the service of the Lord, forgets his material bodily demands.
(Srimad Bhagavatam-----3:28:37-----purport).

Śrīla Rūpa Gosvāmī therefore recommends:
anāsaktasya viṣayān
yathārham upayuñjataḥ
nirbandhaḥ kṛṣṇa-sambandhe
yuktaṁ vairāgyam ucyate
(Bhakti-rasāmṛta-sindhu 1.2.255)
Man and woman should live together as householders in relationship with Kṛṣṇa, only for the purpose of discharging duties in the service of Kṛṣṇa. Engage the children, engage the wife and engage the husband, all in Kṛṣṇa conscious duties, and then all these bodily or material attachments will disappear. Since the via medium is Kṛṣṇa, the consciousness is pure, and there is no possibility of degradation at any time.
(Srimad Bhagavatam-----3:31:42-----purport).