SB 7.4.39

kvacid rudati vaikuṇṭha-
cintā-śabala-cetanaḥ
kvacid dhasati tac-cintā-
hlāda udgāyati kvacit

kvacit—sometimes; rudati—cries; vaikuṇṭha-cintā—by thoughts of Kṛṣṇa; śabala-cetanaḥ—whose mind was bewildered; kvacit—sometimes; hasati—laughs; tat-cintā—by thoughts of Him; āhlādaḥ—being jubilant; udgāyati—chants very loudly; kvacit—sometimes.

Because of advancement in Kṛṣṇa consciousness, he sometimes cried, sometimes laughed, sometimes expressed jubilation and sometimes sang loudly.

This verse further clarifies the comparison of a devotee to a child. If a mother leaves her small child in his bed or cradle and goes away to attend to some family duties, the child immediately understands that his mother has gone away, and therefore he cries. But as soon as the mother returns and cares for the child, the child laughs and becomes jubilant. Similarly, Prahlāda Mahārāja, being always absorbed in thoughts of Kṛṣṇa, sometimes felt separation, thinking, “Where is Kṛṣṇa?” This is explained by Śrī Caitanya Mahāprabhu. Śūnyāyitaṁ jagat sarvaṁ govinda-viraheṇa me. When an exalted devotee feels that Kṛṣṇa is invisible, having gone away, he cries in separation, and sometimes, when he sees that Kṛṣṇa has returned to care for him, he laughs, just as a child sometimes laughs upon understanding that his mother is taking care of him. These symptoms are called bhāva. In The Nectar of Devotion, various bhāvas, ecstatic conditions of a devotee, are fully described. These bhāvas are visible in the activities of a perfect devotee.