Without being eternal, nobody can serve the eternal. That is the Vedic injunction. Without becoming Brahman, one cannot approach the Supreme Brahman. Just like without being fire, nobody can enter into the fire. Without being water, nobody can enter into the water. Similarly, without being fully spiritualized, nobody can enter into the spiritual kingdom. So nitāiyer caraṇa satya: if you catch the lotus feet of Nityānanda, then you become immediately spiritualized.
Just like if you touch electricity, immediately you become electrified. That is natural. Similarly, Nityānanda is eternal happiness. If you touch Nityānanda some way or other, then you become also eternally happy. Tāṅhāra sevaka nitya. Therefore one who has in contact with Nityānanda, they have become eternal.
- nitāiyer caraṇa satya, tāṅhāra sevaka nitya
- dṛḍha kori' dharo nitāir pāy
So just catch Him very tightly.
Narottama boro duḥkhī, nitāi more koro sukhī. At the last, Narottama dāsa Ṭhākura, the composer of this song, he is appealing to Nityānanda: "My dear Lord, I am very unhappy. So You please make me happy. And You kindly keep me in corner of Your lotus feet."
That is the sum and substance of this song.