MM mantra 12

bhava-jaladhim agādhaṁ dustaraṁ nistareyaṁ
katham aham iti ceto mā sma gāḥ kātaratvam
sarasija-dṛśi deve tārakī bhaktir ekā
naraka-bhidi niṣaṇṇā tārayiṣyaty avaśyam
Synonyms: 
bhava — of material existence; jaladhim — the ocean; agādham — fathomless; dustaram — impossible to cross; nistareyam — will cross beyond; katham — how; aham — I; iti — thus; cetaḥ — my dear mind; sma gāḥ — please do not come; kātaratvam — to complete distress; sarasi-ja — like a lotus; dṛśi — whose eyes; deve — unto the Lord; tārakī — deliver; bhaktiḥ — the personality of Devotion; ekā — only; naraka — of the demon Naraka; bhidi — in the destroyer; niṣaṇṇā — reposed; tārayiṣyati — will bring you across; avaśyam — inevitably.
Translation: 
Dear mind, do not bewilder yourself by anxiously thinking, How can I cross this fathomless and impassable ocean of material existence? There is one who can save you—Devotion. If you offer her to the lotus-eyed Lord, the killer of Narakāsura, she will carry you across this ocean without fail.
Purport: 

The devotee is not afraid of the miseries of material existence. He is confident that Kṛṣṇa will save him. Although the forces of destruction are more powerful that any mortal, the devotee is like a tiny bird protected by its parents. The Supreme Lord assures us, "Declare it boldly, O Arjuna, that my devotee never perishes" (Bg. 9.31).

However, if one seeks the protection of the Lord through some means other than devotion, one will fail. Kṛṣṇa is not impressed by anything but devotion. For example, in the Bhagavad-gītā (9.26) He encourages the devotee to offer Him food in order to increase the devotee's loving relationship with Him: "If one offers Me with love and devotion a leaf, a flower, a fruit, or water, I will accept it." The Supreme Lord does not want any food or flowers in and of themselves, but when His devotee offers them with bhakti, He is very attracted and inclined to reciprocate His devotee's love.

Unless the Supreme Lord is pleased with our service, He will not reveal Himself (nāhaṁ prakāśaḥ sarvasya yogamāyā-samāvṛtaḥ [Bg. 7.25]). And without His personal intervention, a soul will remain stranded in the cycle of birth and death, despite all material qualifications. In his prayers to Lord Nṛsiṁha, Prahlāda Mahārāja confirms that bhakti alone can satisfy the Lord: "One may possess wealth, an aristocratic family, beauty, austerity, education, sensory expertise, luster, influence, physical strength, diligence, intelligence, and mystic yogic power, but I think that even by all these qualifications one cannot satisfy the Supreme Personality of Godhead. However, one can satisfy the Lord simply by devotional service. Gajendra did this, and thus the Lord was satisfied with him" (SB 7.9.9).

Even though one is serving a spiritual master, one may doubt the efficacy of bhakti. But King Kulaśekhara assures his mind that there is no need for anxiety. If we contemplate the abysmal depth and impassable breadth of the material ocean, or if we frighten ourselves by dwelling on the torments of hell, then we will become paralyzed and unable to carry out normal activities. There is no need for such fear if one is situated sincerely in devotional service. As the brāhmaṇa from Avantīdeśa said,

etāṁ sa āsthāya parātma-niṣṭhām
adhyāsitāṁ pūrvatamair maharṣibhiḥ
ahaṁ tariṣyāmi duranta-pāraṁ
tamo mukundāṅghri-niṣevayaiva

"I shall cross over the insurmountable ocean of nescience by being firmly fixed in the service of the lotus feet of Kṛṣṇa. This was approved by the previous ācāryas, who were fixed in firm devotion to the Lord, Paramātmā, the Supreme Personality of Godhead" (SB 11.23.57).