The Supreme Personality of Godhead said to the brahmana: I am completely under the control of My devotees. Indeed, I am not at all independent. Because My devotees are completely devoid of material desires, I sit only within the cores of their hearts. What to speak of My devotee, even those who are devotees of My devotee are very dear to Me.
All the great stalwart personalities in the universe, including Lord Brahma and Lord Siva, are fully under the control of the Supreme Personality of Godhead, but the Supreme Personality of Godhead is fully under the control of His devotee.
Why is this? Because the devotee is anyabhilasita-sunya; in other words, he has no material desires in his heart. His only desire is to think always of the Supreme Personality of Godhead and how to serve Him best. Because of this transcendental qualification, the Supreme Lord is extremely favorable to the devotees — indeed, not only the devotees, but also the devotees of the devotees.
Srila Narottama dasa Thakura says, chadiya vaisnava-seva nistara payeche keba: without being a devotee of a devotee, one cannot be released from material entanglement. Therefore Caitanya Mahaprabhu identified Himself as gopi-bhartuh pada-kamalayor dasa-dasanudasah. Thus he instructed us to become not directly servants of Krishna but servants of the servant of Krishna.
Devotees like Brahma, Narada, Vyasadeva and Sukadeva Gosvami are directly servants of Krishna, and one who becomes a servant of Narada, Vyasadeva and Sukadeva, like the six Gosvamis, is still more devoted.
Srila Visvanatha Cakravarti Thakura therefore says, yasya prasadad bhagavat-prasadah: if one very sincerely serves the spiritual master, Krishna certainly becomes favorable to such a devotee.
Following the instructions of a devotee is more valuable than following the instructions of the supreme personality of godhead directly.
Reference: Srimad Bhagavatam 9.4.63