This is the natural result of intense love of Godhead. The devotee does not consider personal inconveniences or impediments. In all circumstances he wants to serve the Supreme Personality of Godhead.
(Sri Caitanya Caritamrta---2:4:186---translation).

Śrīla Bhaktivinoda Ṭhākura summarizes this growth of love of Godhead as a gradual process. A person becomes interested in devotional service by some good fortune. Eventually he becomes interested in pure devotional service without material contamination. At that point, a person wants to associate with devotees. As a result of this association, he becomes more and more interested in discharging devotional service and hearing and chanting. The more one is interested in hearing and chanting, the more he is purified of material contamination. Liberation from material contamination is called anartha-nivṛtti, indicating a diminishing of all unwanted things. This is the test of development in devotional service. If one actually develops the devotional attitude, he must be freed from the material contamination of illicit sex, intoxication, gambling and meat-eating. These are the preliminary symptoms. When one is freed from all material contamination, his firm faith in devotional service awakens. When firm faith develops, a taste arises, and by that taste one becomes attached to devotional service. When this attachment intensifies, the seed of love of Kṛṣṇa fructifies. This position is called prīti or rati (affection) or bhāva (emotion). When rati intensifies, it is called love of Godhead. This love of Godhead is actually life's highest perfection and the reservoir of all pleasure.
(Sri Caitanya Caritamrta---2:23:13---purport).

“Chanting the holy name is the chief means of attaining love of Godhead. This chanting or devotional service does not depend on any paraphernalia, nor on one's having taken birth in a good family. By humility and meekness one attracts the attention of Kṛṣṇa. That is the verdict of all the Vedas. Therefore if one becomes very humble and meek, he can easily attain the lotus feet of Kṛṣṇa in this Age of Kali. That is the fulfillment of all great sacrifices, penances and austerities because when one achieves ecstatic love of Godhead, he attains the complete perfection of life. Therefore whatever one does in executing devotional service must be accompanied by the chanting of the holy name of the Lord.” The chanting of the holy name of Kṛṣṇa—Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare—has been praised by Śrīla Rūpa Gosvāmī in his Nāmāṣṭaka.
(Sri Caitanya Caritamrta---3:4:71---purport).

Unless one has come to the platform of spontaneous love of God, he must follow the regulative principles. Ṭhākura Haridāsa was the living example of how to follow the regulative principles. Similarly, Raghunātha dāsa Gosvāmī was also such a living example. In the Ṣaḍ-gosvāmy-aṣṭaka it is stated, saṅkhyā-pūrvaka-nāma-gāna-natibhiḥ kālāvasānī-kṛtau. The Gosvāmīs, especially Raghunātha dāsa Gosvāmī, strictly followed all the regulative principles. The first regulative principle is that one must chant the Hare Kṛṣṇa mahā-mantra loudly enough so that he can hear himself, and one must vow to chant a fixed number of rounds. Not only was Raghunātha dāsa Gosvāmī chanting a fixed number of rounds, but he had also taken a vow to bow down many times and offer obeisances to the Lord.
(Sri Caitanya Caritamrta---3:11:24---purport).

In the Bhakti-rasāmṛta-sindhu (1.3.1), love of Godhead is compared to sunshine, and this shining makes the devotee's heart more and more lovely. The heart of such a devotee is situated in a transcendental position, beyond even the material mode of goodness. As the devotee's heart becomes increasingly sterilized by the sunshine of love, he attains a state called bhāva. This is the description of bhāva given by Rūpa Gosvāmī. Bhāva is the permanent characteristic of the living entity, and the crucial point of progress for bhāva is called the marginal state of love of Godhead. When the bhāva state becomes deeper and deeper, learned devotees call it love of Godhead.
(Teachings of Lord Caitanya).

Bhāva is the transcendental ecstatic attachment for Kṛṣṇa which results from perfectly understanding that the person Kṛṣṇa and the name Kṛṣṇa are identical. One who has attained bhāva is certainly not contaminated by material nature. He enjoys transcendental pleasure from bhāva, and when bhāva is intensified it is calledlove of Godhead. Lord Caitanya told Prakāśānanda Sarasvatī that the holy name of Kṛṣṇa—the mahā-mantra, or "great chant"—enables anyone who chants it to attain the stage of love of Godhead, or intensified bhāva. Love of Godhead is the ultimate human necessity, for when one compares it with other necessities (namely religion, economic development, sense gratification and liberation), one can see that these others are most insignificant. When one is absorbed in temporary, conditioned existence, he hankers after sense gratification and liberation. But love of Godhead is the eternal nature of the soul; it is unchangeable, without beginning or end.
(Teachings of Lord Caitanya).