In his early life, Bilvamaṅgala Ṭhākura was an impersonalistic monist, and he used to meditate upon the impersonal Brahman effulgence. Later he became a devotee of Lord Kṛṣṇa, and his explanation for this change is given in a verse (text 178) that is quoted in the Bhakti-rasāmṛta-sindhu. Sometimes a devotee gradually comes to the stage of Bhagavān realization, realization of the Supreme Person, after having attained the lower stages of realization — impersonal Brahman realization and localized Paramātmā realization. The condition of such a devotee is described in the Caitanya-candrāmṛta (5), by Prabodhānanda Sarasvatī:

kaivalyaṁ narakāyate tridaśa-pūr ākāśa-puṣpāyate
 durdāntendriya-kāla-sarpa-paṭalī protkhāta-daṁṣṭrāyate
viśvaṁ pūrṇa-sukhāyate vidhi-mahendrādiś ca kīṭāyate
 yat-kāruṇya-kaṭākṣa-vaibhava-vatāṁ taṁ gauram eva stumaḥ

Kaivalya, oneness in the effulgence of Brahman, appears hellish to the devotee. The heavenly planets, the abodes of the demigods, appear to a devotee like phantasmagorias. The yogīs meditate for sense control, but for the devotee the senses appear like serpents with broken teeth. The devotee doesn’t have to control his senses, for his senses are already engaged in the Lord’s service. Consequently there is no possibility that the senses will act like serpents. In the material condition, the senses are as strong as poisonous snakes. But when the senses are engaged in the Lord’s service, they are like poisonous snakes with their fangs removed, and so they are no longer dangerous. The entire world is a replica of Vaikuṇṭha for the devotee because he has no anxiety. He sees that everything belongs to Kṛṣṇa, and he does not want to enjoy anything for himself. He does not even aspire for the position of Lord Brahmā or Indra. He simply wants to engage everything in the service of the Lord; therefore he has no problem. He stands in his original constitutional position. All this is possible when one receives Śrī Caitanya Mahāprabhu’s merciful glance.

In the Caitanya-candrāmṛta there are many more verses illustrating this same principle.

dhik kurvanti ca brahma-yoga-viduṣas taṁ gauracandraṁ numaḥ

(Caitanya-candrāmṛta 6)

tāvad brahma-kathā vimukta-padavī tāvan na tiktī-bhavet
 tāvac cāpi viśṛṅkhalatvam ayate no loka-veda-sthitiḥ
tāvac chāstra-vidāṁ mithaḥ kala-kalo nānā-bahir-vartmasu
 śrī-caitanya-padāmbuja-priya-jano yāvan na dig-gocaraḥ

(Caitanya-candrāmṛta 19)

gauraś cauraḥ sakalam aharat ko ’pi me tīvra-vīryaḥ

(Caitanya-candrāmṛta 60)

A discussion of the impersonal Brahman is not very palatable to a devotee. The so-called regulations of the śāstras also appear null and void to him. There are many people who argue over the śāstras, but for a devotee such discussions are but tumultuous roaring. By the influence of Śrī Caitanya Mahāprabhu, all these problems disappear.