Lord Kṛṣṇa describes this stage of perfection in the Bhagavad-gītā (6.30),
yo māṁ paśyati sarvatra sarvaṁ ca mayi paśyati
tasyāhaṁ na praṇaśyāmi sa ca me na praṇaśyati
"For one who sees Me everywhere and sees everything in Me, I am never lost, nor is he ever lost to Me." Śrīla Prabhupāda writes,
Such a person may appear to see all the separate manifestations of the material nature, but in each and every instance he is conscious of Kṛṣṇa, knowing that everything is a manifestation of Kṛṣṇa's energy." [Bg. 6.30, purport]
This is samādhi, or trance, and whether one achieves it by the eightfold yoga system or by bhakti-yoga, it is the same. In the case of the bhakti-yogī, he is fixed in devotional service at all times, and whatever he sees contributes to his meditation on Kṛṣṇa.
To help us understand pure Kṛṣṇa consciousness, the ācāryas give us examples of samādhi-like states, even in ordinary affairs. When a mother sees the shoes of her little child, she doesn't just perceive them as neutral objects: she feels protection and love for her child. Similarly, when a lover picks up his beloved's comb (especially if he is in separation from her) he may feel intense emotions of love. In the case of Śrī Kṛṣṇa, the Supreme Personality of Godhead, everything is His energy. So wherever the bhakta goes or whatever he perceives throughout the universe, he is reminded of the Lord. Moreover, this recognition is not merely an intellectual habit but a total, overpowering state of love.
In his Brahma-saṁhitā (5.38), Lord Brahmā describes the devotional qualification for seeing Kṛṣṇa always and everywhere:
santaḥ sadaiva hṛdayeṣu vilokayanti
yaṁ śyāmasundaram acintya-guṇa-svarūpaṁ
govindam ādi-puruṣaṁ tam ahaṁ bhajāmi
"I worship Govinda, the primeval Lord, who is Śyāmasundara, Kṛṣṇa Himself, with inconceivable, innumerable attributes, and whom the pure devotees see in their heart of hearts with the eye of devotion tinged with the salve of love."
In his purport, Śrīla Bhaktisiddhānta Sarasvatī writes,
The eye of devotion is nothing but the eye of the pure unalloyed spiritual self of the jīva. The form of Kṛṣṇa is visible to that eye in proportion to its purification by the practice of devotion.
What prevents most of us from seeing Kṛṣṇa with eyes of love? We have a "cataract" on our eyes that consists of our material attachments. As Śrī Kṛṣṇa states,
nāhaṁ prakāśaḥ sarvasya yoga-māyā-samāvṛtaḥ
mūḍho 'yaṁ nābhijānāti loko mām ajam avyayam
"I am never manifest to the foolish and unintelligent. For them I am covered by My internal potency, and therefore they do not know that I am unborn and infallible" (Bg. 7.25). Lord Kṛṣṇa does not hide from us; He wants us to be with Him. He is like the sun that always blazes in the sky. No cloud is big enough to cover the sun, but from our earthly vantage point even a small cloud can block our view of the sun. In the same way, the clouds of our desire and hatred prevent us from seeing our beloved Lord and block us from enjoying the happiness and peace that come from serving Him. To realize Kṛṣṇa consciousness, therefore, we have to rise above our upādhis, the false designations that make us think the body is the self and make us identify with our mental concoctions.
Nārada is describing the ultimate stage of bhakti. This stage is rare, but one can achieve it by the mercy of the Vaiṣṇavas who teach bhakti-yoga. One who reads the Vedic literature with a speculative attitude will never know Kṛṣṇa. But we can attain His grace if we work in bhakti-yoga, guided by His representatives. Śrīla Prabhupāda writes,
When one is fully engaged in Kṛṣṇa consciousness, beginning by chanting the mahā-mantra—Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare—then only can one understand the Supreme Personality of Godhead. [Bg. 7.24, purport]