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MM mantra 33

kṛṣṇa tvadīya-pada-paṅkaja-pañjarāntam
adyaiva me viśatu mānasa-rāja-haṁsaḥ
prāṇa-prayāṇa-samaye kapha-vāta-pittaiḥ
kaṇṭhāvarodhana-vidhau smaraṇaṁ kutas te
Synonyms: 
kṛṣṇa — O Lord Kṛṣṇa; tvadīya — Your; pada — feet; paṅkaja — lotus flower; pañjara — the network; antam — the edge; adya — now, at this moment; eva — certainly; me — my; viśatu — may enter; mānasa — mind; rāja — royal; haṁsa — swan; prāṇa-prayāṇa — of death; samaye — at the time; kapha — mucus; vāta — air; pittaiḥ — and with bile; kaṇṭha — throat; avarodhana-vidhau — when it is choked; smaraṇam — remembrance; kutaḥ — how is it possible; te — of You.
Translation: 
O Lord Kṛṣṇa, at this moment let the royal swan of my mind enter the tangled stems of the lotus of Your feet. How will it be possible for me to remember You at the time of death, when my throat will be choked up with mucus, bile, and air?
Purport: 

Of all the verses of the Mukunda-mālā-stotra, this one was the most beloved of Śrīla Prabhupāda. He frequently quoted it and sang it as a bhajana. On one of the first record albums His Divine Grace produced, he sang this śloka as a complete song. Devotees who served Śrīla Prabhupāda often heard him sing it as he went about his daily activities, or sometimes alone in his room. He also quoted it many times in his purports. Here he explains it in the purport to the second verse of the Eighth Chapter of his Bhagavad-gītā As It Is, in reference to the word prayāṇa-kāla, which carries the same meaning as prāṇa-prayāṇa-samaye in Kulaśekhara's verse:

Now, the word prayāṇa-kāle in this [Bhagavad-gītā] verse is very significant because whatever we do in life will be tested at the time of death. Arjuna is very anxious to know of those who are constantly engaged in Kṛṣṇa consciousness. What should be their position at that final moment? At the time of death all the bodily functions are disrupted, and the mind is not in a proper condition. Thus disturbed by the bodily situation, one may not be able to remember the Supreme Lord. Mahārāja Kulaśekhara, a great devotee, prays, "My dear Lord, just now I am quite healthy, and it is better that I die immediately so that the swan of my mind can seek entrance at the stem of Your lotus feet." The metaphor is used because the swan, a bird of the water, takes pleasure in digging into the lotus flowers; its sporting proclivity is to enter the lotus flower. Mahārāja Kulaśekhara says to the Lord, "Now my mind is undisturbed, and I am quite healthy. If I die immediately, thinking of Your lotus feet, then I am sure that my performance of Your devotional service will become perfect. But if I have to wait for my natural death, then I do not know what will happen, because at that time the bodily functions will be disrupted, my throat will be choked up, and I do not know whether I shall be able to chant Your name. Better let me die immediately."

Later in the Eighth Chapter Lord Kṛṣṇa says that the exact moment of death is crucial: "Whatever state of being one remembers when he quits his body,... that state he will attain without fail" (Bg. 8.6). And in his purports Śrīla Prabhupāda repeatedly recommends chanting the Hare Kṛṣṇa mantra as the best process for remembering Kṛṣṇa at the time of death and successfully transferring oneself to the spiritual world.

The practical difficulty, brought up in Kulaśekhara's verse, is that although it is crucial to remember Kṛṣṇa at the time of death, that time also produces the greatest disruption of one's physical and mental functions. Śrīla Prabhupāda explained that death occurs when the body becomes so painful that the soul finds it unbearable to live in the body any longer. Therefore the paradox: At the time when we should be the most meditative, fixing our mind on Kṛṣṇa and preparing to transfer ourselves to the spiritual world, we are also faced with the greatest possible distraction in the form of agonizing pain. Thus here King Kulaśekhara prays to die now, in good health, so he will be able to absorb his mind in thoughts of Kṛṣṇa's lotus feet.

The ācāryas have assured us that the essence of Kṛṣṇa consciousness is our lifelong devotional activities and sentiments. Kṛṣṇa will not disqualify or discount our accumulated devotional activities due to a last moment epileptic fit or sudden heart failure. Nevertheless, we should always practice chanting Hare Kṛṣṇa so that we will be able to "pass the test" at the end.

In the Īśopaniṣad (17), a devotee requests the Lord: "[At the moment of my death,] please remember all that I have done for You." In his purport Śrīla Prabhupāda informs us that Kṛṣṇa does not have to be reminded; He is the witness within our heart, and He also desires—more than we do—that we come back to Him, back to Godhead. Considering the trauma of death and the dangerous quirks of fate, however, Mahārāja Kulaśekhara prays that he may die immediately rather than wait for old age, when he may forget Kṛṣṇa in the agony of his death throes.