As the trial of Jesus proceeds before the Sanhedrin, the saddest event in the life of Peter takes place. The one who had left everything to follow Our Lord, who had seen so many miracles worked and had received so many tokens of affection, now denies him utterly. He feels himself cornered and even swears he does not know Jesus.
And as Peter was below in the courtyard, one of the maids of the high priest came; and seeing Peter warming himself, she looked at him, and said, ‘You also were with the Nazarene, Jesus.’ But he denied it, saying, ‘I neither know nor understand what you mean.’ And he went out into the gateway. And the maid saw him, and began again to say to the bystanders, ‘This man is one of them.’ But again he denied it. And after a little while again the bystanders said to Peter, ‘Certainly you are one of them; for you are a Galilean.’ But he began to invoke a curse on himself and to swear, ‘I do not know this man of whom you speak.’ 
He denies that he knows his Lord, thereby denying the deepest meaning of his life, which is to be an Apostle and witness of the life of Christ and to proclaim that Jesus is the Son of the living God. His honour, his vocation to be an Apostle, all the hopes that had been placed in him by God, his past and his future, all came tumbling down. How could he possibly have said, I know not this man?
A miracle worked by Jesus a few years before had had for him a deep and special significance. On seeing the miraculous draught of fishes (the first of them), Peter had understood everything; he fell down at Jesus’ knees, saying, ‘Depart from me, for I am a sinful man, O Lord’. For he was astonished ...  It seems that in a flash everything had become clear for him: the holiness of Christ and his own condition as a sinful man. Black stood in clear contrast with white, darkness with light, dirt with cleanness, sin with sanctity. In that moment, whilst his lips were saying that because of his sins he felt unworthy to be close to Our Lord, his eyes, however, and his whole attitude were asking that he might never ever depart from Him. That was such a happy day. That was when everything really began for him: And Jesus said to Simon, ‘Do not be afraid; henceforth you will be catching men.’ And when they had brought their boats to land, they left everything and followed him.  Peter’s life from that moment on would have a most marvellous purpose, that of loving Christ and being a fisher of men. Everything else would serve as a means and an instrument to that end. Yet now, out of weakness and having allowed himself to be overcome by fear and human respect, everything had collapsed.
Sin, infidelity to a greater or lesser degree, always involves a denial of Christ and of that which is most noble within us, a denial of the highest ideals that Christ has sown inside us. Sin is the great downfall of man. This is why we need to struggle with determination, counting on grace, so that we avoid all grave sins, whether of malice, weakness or culpable ignorance, and then all deliberate venial sin.
But even from our sins, when we are unfortunate enough to commit them, we have to draw advantage, because contrition strengthens the bonds of our friendship with Our Lord. Our mistakes should never discourage us, provided we act with humility. A sincere act of repentance is always the occasion of a new encounter with Our Lord, from which we can derive some completely unsuspected consequences for our interior lives. If we sin, we have to come back again to Our Lord as often as is necessary, without getting anxious, although certainly with sorrow. Peter took an hour to fall; but in an instant he rights himself and sets about raising himself higher than he was before his fall. 
Heaven is full of great sinners who decided to repent. Jesus always welcomes us and rejoices to see us set out again upon the road we had abandoned, perhaps in small matters.
The look of Jesus and Peter’s contrition.
Jesus, having been much ill-used, is led into one of the courtyards. He then turned and looked at Peter.  Their looks meet. Peter would like to bow his head, but he cannot tear his eyes from Him, Whom he has just denied. He knows the Saviour’s looks well; that look that had determined his vocation, he had not been able to resist either its authority or its charm; and that tender look of the Master’s on the day He had affirmed, looking at His disciples, ‘Here are my brethren, my sisters, my mother!’ And that look that had made him tremble when he, Simon, had wanted to banish the Cross from Jesus’ path! And the affectionately pitying look with which he had invited the too-rich young man to follow him! And His look, clouded with tears, before Lazarus’ tomb ... He knows them well, the Saviour’s looks.
And yet never, never had he seen on the Saviour’s face the expression he sees there at this moment, the eyes marked with sadness but without any severity. A look of reproach, without a doubt, but which becomes suppliant at the same time and seems to repeat to him, ‘Simon, I have prayed for thee!’
This look only rests on him for an instant; Jesus is violently dragged away by the soldiers, but Peter sees Him all the time.  He sees that compassionate look of Jesus fixed upon the deep wound of his guilt. He now understands the enormity of his sin, and the fulfilment of Our Lord’s prophecy about his betrayal. And Peter remembers the words of Our Lord, ‘Before the cock crows today, you will deny me three times.’ And he went out and wept bitterly.  His going out was to acknowledge his fault. He was able to weep bitterly because he knew how to love; the bitterness of sorrow in him quickly gave way to the sweetness of love. 
Knowing that Our Lord had looked upon him prevented Peter from falling into despair. His look was one of encouragement in which Peter felt understood and forgiven. How it would remind him of the parables of the Good Shepherd, the Prodigal Son and the Lost Sheep!
Peter went out. He moved away from that whole situation, in which he had imprudently placed himself, so as to avoid any possible relapses. He realised that this was not the place for him to be. He remembered his Lord and he wept bitterly. We see ourselves in the situation of Peter. Sorrow of Love – Because He is good. Because He is your Friend, Who gave His life for you. Because everything good you have is His. Because you have offended Him so much ... Because He has forgiven you ... He! Forgiven you!
Weep, my son, with sorrow of Love. 
Contrition gives special strength to the soul; it restores hope, makes the Christian forget himself and draw close to God once more with a deeper act of love. Contrition proves the quality of interior life and always attracts God’s mercy; ... this is the man to whom I will look, he that is humble and contrite in spirit ... 
Christ found no difficulty in building his Church upon a man who was able to fall and who did fall. God also counts on weak instruments, provided they repent, to carry out his big project: the salvation of mankind.
It is very probable that after the denials and his repentance Peter would have gone to look for our Blessed Lady. This is what we do also at this moment as our own faults and denials come more vividly to mind.
True repentance. Acts of contrition.
As well as giving the soul great strength, true contrition also brings special happiness and enables us to be effective in our dealings with others. The Master passes very close to us, again and again. He looks at us ... And if you look at him, if you listen to him, if you don’t reject him, He will teach you how to give a supernatural meaning to everything you do ... Then you too, wherever you may be, will sow consolation and peace and joy. 
Our Lord also looked at Judas, who was encouraged to come back in the moment of the betrayal and could hear Our Lord calling him friend. Friend, why are you here? In this moment he did not repent, although later he did. When he saw that he was condemned, he repented and brought back the thirty pieces of silver 
What a contrast between Peter and Judas! Both in different ways betray their fidelity to their Master. Both repent. Peter, in spite of his denials, will become the rock upon which the Church of Christ will be set until the end of time. Judas went and hanged himself. Human repentance alone is not enough; it produces anxiety, bitterness and despair.
Linked to Christ repentance is turned into a joyous sorrow, because a lost friendship is regained. Peter is united to Our Lord in an instant, and much closer than he had ever been before, because of his sorrow for his denials. Out of his denials is born a faithfulness that will take him even to martyrdom.
With Judas it is just the opposite, and he is left on his own: What is that to us? See to it yourself, the chief priests tell him. In the isolation brought about by sin, Judas would not go to Christ. He had lost hope.
We need to awaken frequently in our hearts a sorrow, born out of Love, for the sins we have committed. This we should do especially as we make our examination of conscience at the end of each day, and when we prepare ourselves for Confession.
You who tend to lose heart, I will tell you something that is very consoling: when a person does what he can, God will not deny his grace. Our Lord is a Father, and if, in the silence of his heart, one of his sons says to him: ‘My Father in Heaven, here I am, help me ... ‘ If he goes to the Mother of God, who is our Mother, he will get through.