Śrīla Bhakti Sundar Govinda Dev-Goswāmī Mahārāj shows the highest development of śaraṇāgati.
The mahāmantra can give us everything. It has that type of power. Mahāprabhu said in His Śikṣāṣṭakam (1):
cheto-darpaṇa‑mārjanaṁ bhava-mahādāvāgni-nirvāpaṇaṁ
śreyaḥ-kairava-chandrikā-vitaraṇaṁ vidyā-vadhū-jīvanam
ānandāmbudhi-vardhanaṁ-prati-padaṁ pūrṇāmṛtāsvādanaṁ
sarvātma-snapanaṁ paraṁ vijayate śrī‑kṛṣṇa‑saṅkīrtanam
[“Śrī Kṛṣṇa‑saṅkīrtan cleanses the mirror of consciousness, extinguishes the raging forest fire of material existence, shines moonlight on the evening lotus of good fortune, is the life of those enlightened with paramour love for the Lord, expands the ocean of ecstasy, is the taste of full nectar at every moment, and soothes the entire self. May Śrī Kṛṣṇa‑saṅkīrtan be supremely victorious!”]
Śrī Chaitanya Mahāprabhu appeared in this Kali-yuga. He is Himself Rādhā‑Kṛṣṇa, but for the conditioned souls, He also appeared as a Yuga-avatār. That is His outward aspect for this mundane world. Kṛṣṇa came for two causes: (1) to preach Hari-nām-saṅkīrtan to the jīva-souls, and (2) to take and enjoy the mood and colour of Rādhārāṇī.
hariḥ puraṭa‑sundara-dyuti-kadamba-sandīpitaḥ
sadā hṛdaya-kandare sphuratu vaḥ śachī-nandanaḥ
(Śrī Chaitanya-charitāmṛta: Ādi-līlā, 1.4)
[“May that beautiful, golden, radiant Lord, Śrī Śachī Nandan, always be manifest in the core of your heart.”]
Mahāprabhu said, “We can get everything through the Hare Kṛṣṇa mahāmantra”, but pāñcharātrik dīkṣā [‘second initiation’] also helps that. We see that in the scriptures there are some rules and regulations for pāñcharātrik dīkṣā. If we can properly follow them, then help will come to us from the transcendental world. Kṛṣṇa‑mantra is the seed of all mantras, and the seed of Kṛṣṇa‑mantra is Om. This word first appeared in the mundane world through Brahmā, and Brahmā meditated on it. Then all the other mantras came. Mahāprabhu Himself showed us that we must offer ourselves through the mantram. That is the meaning of the mantram actually.
One day in the evening, while Śrīla Saraswatī Ṭhākur was chanting Hari-nām on his beads, two sannyāsīs were trying to understand the meaning of Kṛṣṇa‑mantram, in particular the word Gopī-jana-vallabhāya. Prabhupād said, “It is in nimitārthe chaturthī”, which means offering oneself for that cause. So, “I am offering myself for that purpose [that of Gopī-jana-vallabha—the gopīs Beloved].”
You will see the great meaning of this through Śrīman Mahāprabhu in Chaitanya-charitāmṛta.
dīkṣā‑kāle bhakta kare ātma-samarpaṇa
sei-kāle kṛṣṇa tāre kare ātma-sama
sei deha kare tāra chid-ānandamaya
aprākṛta-dehe tā̐ra charaṇa bhajaya
(Śrī Chaitanya-charitāmṛta: Antya-līlā, 4.192–3)
[“At the time of initiation, a devotee fully surrenders themself. Kṛṣṇa then accepts them and makes their body spiritual and joyful, and they serve His feet in that supramundane body.”]
When a devotee offers themself with their full energy, body, mind, and soul, then Kṛṣṇa looks at their devotion, and He Himself takes everything from them. In Śrīmad Bhagavad-gītā (18.66), you have heard,
sarva-dharmān parityajya mām ekaṁ śaraṇaṁ vraja
“I am only the person who can give you relief and ecstasy. So, take shelter of Me.”
This is the first stage of śaraṇāgati [surrender], and that takes us up to Vraja-vadhū-vargena yā kalpita: the way the gopīs worship and satisfy Lord Kṛṣṇa in Vraja Dhām. That type of service chance will come to us, and that is supreme, that gopī-bhāva.
We are getting gopī-bhāva through this mantram, and we must serve Kṛṣṇa in this way. We need entrance and service in that world. This is the meaning of Kṛṣṇa‑mantram actually.
I shall give you what I got from my Guru Mahārāj, Śrīla Bhakti Rakṣak Śrīdhar Dev-Goswāmī Mahārāj, what Śrīla Guru Mahārāj got from Śrīla Saraswatī Ṭhākur, what Śrīla Saraswatī Ṭhākur got from Śrīla Bhakti Vinod Ṭhākur and Śrīla Gaura Kiśor Dās Bājājī Mahārāj. This is our preceptorial line from down to up. From up to down, this mantram has come from Bhagavān Śrī Kṛṣṇa to Brahmā, from Brahmā to Nārad, Nārad to Vyāsadev, and Vyāsadev to Madhva Āchārya. Through this preceptorial line, this seed came down to Mādhavendra Purī, and he planted it very nicely. In this way it took the form of Kṛṣṇa‑prema and came through Mādhavendra Purī to Īśvara Purī and Śrī Chaitanya Mahāprabhu. Śrīman Mahāprabhu then showed us how we should plant this beautiful, transcendental tree, this creeper of devotion, through this mantram.
I have got from Śrīla Guru Mahārāj this charge to spread this mantram and Kṛṣṇa consciousness in this mundane world. So, it is my duty to give it to souls who are surrendered to Kṛṣṇa. You are surrendered to Kṛṣṇa. So, I am giving this mantram, which I have got from my Guru Mahārāj, to you.
Source
Spoken 2 April 1991.
References
ārādhyo bhagavān vrajeśa-tanayas tad-dhāma vṛndāvanam
ramyā kāchid upāsanā vraja-vadhū-vargeṇā yā kalpitā
śrīmad-bhāgavataṁ pramāṇam amalaṁ premā pumartho mahān
śrī-chaitanya-mahāprabhor matam idaṁ tatrādaraḥ naḥ paraḥ
(Śrīla Śrīnāth Chakravartī)
“‘The worshippable Supreme Lord is the son of the King of Vraja, Kṛṣṇa, whose abode is Vṛndāvan. The most pleasing worship is that performed by the wives of Vraja. Śrīmad Bhāgavatam is the flawless authority, and divine love is the ultimate goal of human life.’ This is the conception of Śrī Chaitanya Mahāprabhu. We adore it as supreme.”