The servitude to Śrīmatī Rādhārāṇī

Prabodhānanda Sarasvatī, once the spiritual guide of sixty thousand ascetics, elaborates on the servitude to Śrīmatī Rādhārāṇī "the most uncommon and elevated of all spiritual goals" in his Vṛndāvana-mahimāmṛta ("Nectar of the Greatness of Vṛndāvana"):

dhanyo loke mumukñur hari-bhajana-paro dhanya-dhanyas tato'sau
dhanyo yaḥ kṛñṇa-pādāmbuja-rati-paramo rukmiṇīśa-priyo'taḥ |
yāśodeya-priyo'taḥ subala-suhṛd ato gopakāntā-priyo'taḥ
śrīmad-vṛndāvaneśvary-atirasa-vivaśa-vivaśārādhakaḥ sarva-mūrdhni || 2.35.

Glorious are those persons who desire to climb out of the well of material existence and attain liberation;
even more glorious are those who have dedicated themselves to the service of the Lord.
More elevated again are those who have become attached to Śrī Kṛñṇa's lotus feet.
Those who love the husband of the Queen Rukmiṇī are superior again to such devotees, while
more praiseworthy still are those who are dear to the son of Yaśodā.
More glorious again are those who have made friends with Subala's comrade.
Superior to those in the mood of friendship are those who worship the Lord as the lover of the gopīs.
Yet standing at the head of all devotees in the creation are those whose thoughts have been washed away by the flood of sacred rapture emanating from the daughter of King Vṛñabhānu, Rādhā, and worship her above all.14

That devotion that has been described in the introductory verse to the Vidagdha-mādhava (and then quoted in the Caitanya-caritāmṛta) as "the most elevated of all sacred erotic raptures" is this affection of Rādhārāṇī's girlfriends, who care even more for her than they do for Kṛñṇa himself. Their bhāvollāsā rati-a mood of constant exultation in Rādhā's divine feelings for Kṛñṇa-is the crown jewel of all mystic achievements. It is the priceless boon of Caitanya Mahāprabhu's limitless mercy.

anarpita-carīṁ cirāt karuṇayāvatīrṇaḥ kalau
samarpayitum unnatojjvala-rasāṁ sva-bhakti-śriyām |
hariḥ puraṭa-sundara-dyuti-kadamba-sandīpitaḥ
sadā hṛdaya-kandare sphuratu vaḥ śacī-nandanaḥ || Vidagdha-mädhava 1.2 (CC 1.3.2).

This elevated, effulgent, taste of sacred rapture is the wealth of devotional love;
the Lord never gives it at any time; yet, out of his mercy, he came in this Age of Quarrel to distribute this treasure to the world, becoming manifested in his golden form.
The son of Śacī is like a lion; may he dwell in your hearts forever.