Summary: Material desires can easily draw us to the position of being taken far from the path of devotional life. A sincere devotee is quite aware of this danger, and takes all precautions to not indulge; even a small indulgence very quickly draws one into significant foolishness! To receive the Lord's protection from these desires, we need to be very very sincere in our purpose! Due to the amazingly merciful nature the Supreme Lord, recognizing our deeper sincerity of purpose, He may, according to His sweet will, both provide us with the means to see our desires fulfilled (as the cow supplies milk to the calf), but also supply protection from the sense gratification component of consciousness when coming in contact with the very object of those desires (as the cow protects her calf).
Dhruva recognizes this amazingly merciful nature of the Lord, just by dint of the purity he has received from the mercy which came from Narada, and the purification received from the devotional service rendered under the direction of Narada. He is feeling *extremely grateful* for this mercy of Narada! To qualify ourselves for this unique mercy of the Lord, as Dhruva did, what must each of us do? We must place ourselves in the care of Sri Naradaji or his representative, which means we must sincerely carry out the instructions we receive from such representative, stirred by feelings of great gratitude in our hearts for the mercy received. That was Dhruva's qualification, and it needs to become ours.
a) Srimad-Bhagavatam 4.9.17
TRANSLATION My Lord, O Supreme Lord, You are the supreme personified form of all benediction. Therefore, for one who abides in Your devotional service with no other desire, worshiping Your lotus feet is better than becoming king and lording it over a kingdom. That is the benediction of worshiping Your lotus feet. To ignorant devotees like me, You are the causelessly merciful maintainer, just like a cow, who takes care of the newly born calf by supplying milk and giving it protection from attack.
PURPORT Dhruva Maharaja was cognizant of the defective nature of his own devotional service. Pure devotional service is without material form and is not covered by mental speculation or fruitive activities. Pure devotional service is therefore called ahaituki, unmotivated. Dhruva Maharaja knew that he had come to worship the Lord in devotional service with a motive - to get the kingdom of his father. Such an adulterated devotee can never see the Supreme Personality of Godhead face to face. He therefore felt very grateful for the causeless mercy of the Lord. The Lord is so merciful that not only does He fulfill the desires of a devotee who is driven by ignorance and desires for material benefit, but He also gives such a devotee all protection, just as a cow gives milk to a newly born calf.
In the Bhagavad-Gita it is said that the Lord gives intelligence to the constantly engaged devotee so that he may gradually approach the Lord without difficulty. A devotee must be very sincere in his devotional service; then, although there may be many things wrong on the devotee's part, Krsna will guide him and gradually elevate him to the highest position of devotional service. The Lord is addressed herein by Dhruva Maharaja as purusartha-murti, the ultimate goal of life. Generally purusartha is taken to mean execution of a type of religious principle or worship of God in order to get material benediction. Prayers for material benediction are intended for satisfying the senses. And when one is frustrated and cannot fully satisfy the senses in spite of all endeavor, he desires liberation, or freedom from material existence. These activities are generally called purusartha. But actually the ultimate goal is to understand the Supreme Personality of Godhead. This is called pancama-purusartha, the ultimate goal of life. Lord Caitanya therefore taught us not to ask from the Supreme Personality any benediction such as material wealth, popularity or a good wife. One should simply pray to the Lord to be constantly engaged in His transcendental loving service. Dhruva Maharaja, being cognizant of his desire for material benefit, wanted protection from the Lord so that he might not be misled or deviated from the path of devotional service by material desires.