To be fully absorbed in the thought of Kṛṣṇa means clearance of material dirts or hankerings. As a very rich man has no hankerings for small petty things, so also a devotee of Lord Kṛṣṇa, who is guaranteed to pass on to the kingdom of God, where life is eternal, fully cognizant and blissful, naturally has no hankerings for petty material things, which are like dolls or shadows of the reality and are without permanent value. That is the sign of spiritually enriched persons. And in due course of time, when a pure devotee is completely prepared, all of a sudden the change of body occurs which is commonly called death.
(Srimad Bhagavatam---1:6:27---purport).

The only purpose of life is to be fully absorbed in thoughts of Kṛṣṇa and His form, pastimes, activities and qualities. If one is able to think of Kṛṣṇa in this way, twenty-four hours a day, he is already liberated (svarūpeṇa vyavasthitiḥ (S.B.-2:10:6). Whereas materialists are absorbed in material thoughts and activities, devotees, on the contrary, are always absorbed in thoughts of Kṛṣṇa and Kṛṣṇa's activities. Therefore they are already on the platform of liberation. One has to think of Kṛṣṇa with full absorption at the time of death. Then he will certainly return home, back to Godhead, without a doubt.
(Srimad Bhagavatam---5:19:13---purport).

A devotee is always transcendentally situated. paraṁ dṛṣṭvā nivartate: (B.G.-5:59) one who has seen the Supreme Personality of Godhead is no longer interested in material sense enjoyment. Even such an exalted devotee as Dhruva Mahārāja went to the forest for the sake of material benefit, but when he actually saw the Supreme Personality of Godhead, he refused to accept any material benediction. He said, svāmin kṛtārtho 'smi varaṁ na yāce: (CC-2:22:42) "My dear Lord, I am fully satisfied with whatever You have given me or not given me. I have nothing to ask from You, for I am fully satisfied to be engaged in Your service." This is the mentality of a pure devotee, who does not want anything, material or spiritual, from the Personality of Godhead. Our Kṛṣṇa consciousness movement is therefore called kṛṣṇa-bhāvanāmṛta-saṅgha, the association of persons who are simply satisfied inthoughts of Kṛṣṇa. Being absorbed in thoughts of Kṛṣṇa is neither expensive nor troublesome.
(Srimad Bhagavatam---9:9:45---purport).

Prahlāda Mahārāja was always absorbed in thought of Kṛṣṇa. Thus, being always embraced by the Lord, he did not know how his bodily necessities, such as sitting, walking, eating, lying down, drinking and talking, were being automatically performed.
A small child, while being cared for by his mother, does not know how the needs of the body for eating, sleeping, lying down, passing water and evacuating are being fulfilled. He is simply satisfied to be on the lap of his mother. Similarly, Prahlāda Mahārāja was exactly like a small child, being cared for by Govinda. The necessary activities of his body were performed without his knowledge. As a father and mother care for their child, Govinda cared for Prahlāda Mahārāja, who remained always absorbed in thoughts of Govinda. This is Kṛṣṇa consciousness. Prahlāda Mahārāja is the vivid example of perfection in Kṛṣṇa consciousness.
(Srimad Bhagavatam----7:4:38---translation and purport).

When Akrūra came to Vṛndāvana in search of Kṛṣṇa, he saw the footprints of the Lord on the dust of Nanda-grāma and at once fell on them in ecstasy of transcendental love. This ecstasy is possible for a devotee who is fully absorbed in incessant thoughts of Kṛṣṇa. Such a pure devotee of the Lord is naturally faultless because he is always associated with the supremely pure Personality of Godhead. Constant thought of the Lord is the antiseptic method for keeping oneself free from the infectious contamination of the material qualities. The pure devotee of the Lord is always in company with the Lord by thinking of Him. Yet, in the particular context of time and place, the transcendental emotions take a different turn, and this breaks the mental equilibrium of the devotee. Lord Caitanya displayed the typical example of transcendental ecstasy, as we can understand from the life of this incarnation of God.
(Srimad Bhagavatam---3:1:32---purport).