Drona had proposed to form the army in a half Sakata (wheel) and half lotus array.  Among the leaves of the lotus, at the centre of it, would be formed an array of a needle, with Karna, Bhurisravas, Aswatthaman, Vrishasena, Kripa and Salya standing guard around Jayadratha, who would be placed inside the eye of the needle (sucya vyuha).  If one has to gain an insight into the impossibility of the task at hand, one has to see the size of the army that surrounded Jayadratha.

dīrgho dvādaśa gavyūtiḥ pañcārdhe pañca vistṛtaḥ
vyūhaḥ sacakraśakaṭo bhāradvājena nirmitaḥ

is what Drona tells Jayadratha.    “Bharadwaja's son, O king, said these words unto Jayadratha.  ’Thyself, Somadatta's son, the mighty car-warrior Karna, Aswatthaman, Salya, Vrishasena and Kripa, with a hundred thousand horse, sixty thousand cars, four and ten thousand elephants with rent temples, one and twenty thousand foot-soldiers clad in mail take up your station behind me at the distance of twelve miles” (Mahabharata, Book 7, Chapter 63 in Sanskrit and 87 in English).  The protective wall around Jayadratha was twelve miles thick. The entire Army of Duryodhana occupied a length of forty-eight miles with a rear guard of twenty miles deep.  If Jayadratha was placedat the centre of the whole array, then this would mean that Arjuna had to penetrate an army of (a minimum of) twenty-four miles deep before he could reach the six maharatas that guarded Jayadratha, after crossing whom alone could he reach the target and accomplish the task at hand.  And to achieve this he had set himself a deadline of twelve hours!  A deadline in its real sense of the word.  You either reach the line or you are dead.  The immensity is dreadful indeed!  No wonder that even the very Lord was alarmedat the size of the task and the possible consequence of a failure.  Take a look at the way he admonishes, censures Arjuna:

“After Partha had vowed the death of the ruler of the Sindhus, the mighty-armed Vasudeva addressed Dhananjaya and said,--With the consent of thy brothers (alone, but without consulting me), thou hast sworn, saying--I will slay the ruler of the Sindhus! This hath been an act of great rashness (on thy part)! Without consulting me, thou hast taken up a great weight (upon thy shoulders)! Alas, how shall we escape the ridicule of all men?” (Mahabharata, Book 7, Chapter 75)

‘I do not approve of your act, which I consider as nothing but rash.  You should have consulted me before accepting such a heavy burden on yourself Arjuna!  My spies inform me of the immensity of the task before us.  And the time for achieving the goal is very short.  Arjuna, I do not see how we are going to succeed in achieving your vow!’  Every word is doused in anxiety.  It is one of those very strange and rare instances where we see Lord Krishna agitated and shaken.  Or was he really shaken!

Not so for Arjuna.  He remained cool.  ‘The combined energy of those six great car-warriors you mentioned does not measure even up to half of mine.  Krishna!  You are going to see all of them standing weaponless and baffled tomorrow!  Krishna, that is not impossible for me for—

 tathā prabhāte kartāsmi yathā kṛṣṇa suyodhanaḥ
 nānyaṃ dhanurdharaṃ loke maṃsyate matsamaṃ yudhi

gāṇḍīvaṃ ca dhanur divyaṃ yoddhā cāhaṃ nararṣabha
 tvaṃ ca yantā hṛṣīkeśa kiṃ nu syād ajitaṃ mayā
(Mahabharata, Book 7, Sloka 49-50, Chapter 53 in Sanskrit and 76 in English)

I am going to show to Duryodhana that there is no other bowman in the world that equals me.  Vasudeva!  The warrior is me, Arjuna and the weapon is nothing other than Gandiva, the celestial bow.  Hrishikesa, over and above these two, I have YOU as my charioteer.  How is that victory cannot be mine!

How can I fail, when you are my guide, who leads my way!  God!  I don’t know what God felt about that answer, but I am really stupefiedat the kind of trust and faith residing in those words.  Incomparable faith at such stressful times!  May the Lord be merciful to grant one-hundred-thousandth of that faith, to me and to every one of us!

So saying, Arjuna went to sleep.  He, who had lost his son in battle, in the most callous manner possible, went to sleep. Before going to sleep he told the Lord to go and console Kunti, Subhadra and Uttara.   I am quoting from Vyasa: “'Go, and comfort thy sister Subhadra with her daughter-in-law.  And, O Madhava, let also that daughter-in-law, and her companions, be comforted by thee; O lord, comfort them with soothing words that are again fraught with truth.' Thus addressed, Vasudeva, with a cheerless heart, wending to Arjuna's abode, began to comfort his sorrowing sister afflicted with grief on account of the death of her son.” (Mahabharata, Book 7, Chapter 77).

Arjuna, on whose shoulders rested an immense burden walked away in peace to his bed, leaving it for the Lord to console Subhadra and Uttara, Arjuna’s wife and daughter-in-law!

source; chennai online