The great devotee Uddhava once wrote a letter to Kṛṣṇa: "My dear Kṛṣṇa, I have just finished the study of all kinds of philosophical books and Vedic verses about the goal of life, and so now I have a little reputation for my studies. But still, in spite of my reputation, my knowledge is condemned, because although enjoying the effulgence of Vedic knowledge, I could not appreciate the effulgence emanating from the nails of Your toes. Therefore, the sooner my pride and Vedic knowledge are finished, the better it will be!" This is an example of indifference.
Another devotee very anxiously expressed himself thusly: "My mind is very flickering, so I cannot concentrate it upon Your lotus feet. And seeing this inefficiency in myself I become ashamed, and the whole night I am unable to sleep because I am exasperated by my great inability."
In the Kṛṣṇa-karṇāmṛta Bilvamaṅgala Thākur has explained his restlessness as follows: "My dear Lord, Your naughtiness in boyhood is the most wonderful thing in the three worlds. And You Yourself know what this naughtiness is. As such, You can very easily understand my flickering mind. This is known to You and myself. Therefore, I am simply yearning to know how I can fix my mind on Your lotus feet."
Another devotee expressed his impudency by saying: "My dear Lord, without considering my lowly position, I must confess to You that my eyes are just like black wasps, desiring to hover at Your lotus feet."
In the Seventh Canto of Śrīmad-Bhāgavatam, 4th Chapter, 27th verse, the great sage Nārada informs Mahārāj Yudhiṣṭhira about Prahlāda Mahārāj, who was a devotee from the very beginning of his life. The proof of Prahlāda's natural devotion is that even when he was a small child he did not play with his playmates, but was always eager to preach the glories of the Lord. Instead of joining in their sportive acrobatic feats, he remained as an inactive child because he was always in trance, meditating on Kṛṣṇa. As such, there was no possibility of his being touched by the external world.
The following statement is about a brāhmaṇa devotee: "This brāhmaṇa is very expert in all kinds of activities, but I do not know why he is looking up without moving his eyes. It appears that his body is fixed motionless just like a doll's. In this condition, I can guess that he has been captivated by the transcendental beauty of that expert flute-player, Śrī Kṛṣṇa, and, being attached to Him, he is simply staring at the black cloud, remembering the bodily hue of Śrī Kṛṣṇa." This is an example of how a devotee can become inert due to ecstatic love.
In the Śrīmad-Bhāgavatam, Seventh Canto, 4th Chapter, 30th verse, Prahlāda Mahārāj says that even in his childhood, when he was loudly speaking the glories of the Lord, he used to dance just like a shameless madman. And sometimes, being fully absorbed in thought on the pastimes of the Lord, he used to imitate such pastimes. This is an instance of a devotee's being almost like a madman. Similarly, it is said that the great sage Nārada was so ecstatically in love with Kṛṣṇa that he would sometimes dance naked, and sometimes his whole body would become stunned. Sometimes he would laugh very loudly, sometimes he would cry very loudly, sometimes he would remain silent, and sometimes he would appear to be suffering from some disease, although he had no disease. This is another instance of becoming like a madman in the ecstasy of devotion.
In the Hari-bhakti-sudhodaya it is stated that when Prahlāda Mahārāj was thinking himself unfit to approach the Supreme Personality of Godhead, he immersed himself in great distress, in an ocean of unhappiness. As such, he used to shed tears and lie down on the floor as though unconscious.
The students of a great devotee once talked amongst themselves in this way: "My dear Godbrothers, our spiritual master, after seeing the lotus feet of the Lord, has thrown himself into the fire of lamentation, and because of this fire the water of his life has almost dried away. Let us now pour the nectar of the holy name through his ears, and by doing so the swan of his life may again show signs of life."
When Lord Kṛṣṇa went to the city of Śoṇitapura to fight with Bali's son Bāṇa and to cut off all his hands, Uddhava, being separated from Kṛṣṇa and thinking of His fight, was almost completely stunned into unconsciousness.
When a devotee is fully in love with the Supreme Personality of Godhead, there may be the following symptoms due to his feelings of separation from the Lord: feverish condition of the body, withering of the body, lack of sleep, nonattachment, inertness, appearing diseased, madness, unconsciousness and sometimes death.