Śrīla Śrīnivāsa Ācārya has sung:
nānā-śāstra-vicāraṇaika-nipuṇau sad-dharma-saṁsthāpakau
lokānāṁ hita-kāriṇau tri-bhuvane mānyau śaraṇyākarau
rādhā-kṛṣṇa-padāravinda-bhajanānandena mattālikau
vande rūpa-sanātanau raghu-yugau śrī-jīva-gopālakau

The six Gosvāmīs, under the direction of Śrīla Rūpa Gosvāmī and Śrīla Sanātana Gosvāmī, studied various Vedic literatures and picked up the essence of them, the devotional service of the Lord. This means that all the Gosvāmīs wrote many scriptures on devotional service with the support of the Vedic literature. Devotional service is not a sentimental activity. The essence of Vedic knowledge is devotional service, as confirmed in the Bhagavad-gītā (15.15): vedaiś ca sarvair aham eva vedyaḥ. All the Vedic literature aims at understanding Kṛṣṇa, and how to understand Kṛṣṇa through devotional service has been explained by Śrīla Rūpa and Sanātana Gosvāmīs, with evidence from all Vedic literatures. They have put it so nicely that even a rascal or first-class fool can be delivered by devotional service under the guidance of the Gosvāmīs.
(Sri Caitanya Caritamrta-2:1:33-purport).

The Gosvāmīs carried out the preaching work of devotional service on the basis of an analytical study of all confidential Vedic literatures. This was in compliance with the order of Śrī Caitanya Mahāprabhu. Thus one can understand the most confidential devotional service of Vṛndāvana.
This proves that bona fide devotional service is based on the conclusions of the Vedic literature. It is not based on the type of sentiment exhibited by the prākṛta-sahajiyās. The prākṛta-sahajiyās do not consult the Vedic literatures, and they are debauchees, woman-hunters and smokers of gañjā. Sometimes they give a theatrical performance and cry for the Lord with tears in their eyes. Of course, all scriptural conclusions are washed off by these tears. The prākṛta-sahajiyās do not realize that they are violating the orders of Śrī Caitanya Mahāprabhu, who specifically said that to understand Vṛndāvana and the pastimes of Vṛndāvana one must have sufficient knowledge of the śāstras (Vedic literatures). As stated in Śrīmad-Bhāgavatam (1.2.12), bhaktyā śruta-gṛhītayā. This means that devotional service is acquired from Vedic knowledge. Tac chraddadhānāḥ munayaḥ. Devotees who are actually serious attain bhakti, scientific devotional service, by hearing Vedic literatures (bhaktyā śruta-gṛhītayā). It is not that one should create something out of sentimentality, become a sahajiyā and advocate such concocted devotional service. However, Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura considered such sahajiyās to be more favorable than the impersonalists, who are hopelessly atheistic. The impersonalists have no idea of the Supreme Personality of Godhead. The position of the sahajiyās is far better than that of the Māyāvādī sannyāsīs. Although the sahajiyās do not think much of Vedic knowledge, they nonetheless have accepted Lord Kṛṣṇa as the Supreme Lord. Unfortunately, they mislead others from authentic devotional service.
(Sri Caitanya Caritamrta-2:1:34, translation and purport).

Devotional service is not a matter of sentimental speculation or imaginative ecstasy. Its substance is practical activity. Śrīla Rūpa Gosvāmī, in his Bhakti-rasāmṛta-sindhu (1.1.11), has defined devotional service as follows:
anyābhilāṣitā-śūnyaṁ
jñāna-karmādy-anāvṛtam
ānukūlyena kṛṣṇānu-
śīlanaṁ bhaktir uttamā
(Sri caitanya Caritamrta-2:19:167)
"Uttamā bhakti, or unalloyed devotion unto the Supreme Personality of Godhead, Śrī Kṛṣṇa, involves the rendering of devotional service in a way that is favorable to the Lord. This devotional service should be free from any extraneous motive and devoid of fruitive karma, impersonal jñāna and all other selfish desires."
Bhakti is a sort of cultivation. As soon as we say "cultivation," we must refer to activity. Cultivation of spirituality does not mean sitting down idly for meditation, as some pseudo-yogīs teach. Such idle meditation may be good for those who have no information of devotional service, and for this reason it is sometimes recommended as a way to check distracting materialistic activities. Meditation means stopping all nonsensical activities, at least for the time being. Devotional service, however, not only puts an end to all nonsensical mundane activities, but also engages one in meaningful devotional activities.
(Nectar of Instruction,3-purport).