Jesus and eleven disciples had left the Upper Room; the Passover meal was over and they walked in the darkness to the Mount of Olives (Matthew 26:30).  Judas Iscariot had gone to do his evil business immediately after taking the bread (John 13:26-30): interestingly he did not take the wine from the cup of redemption.  More evil was waiting to tempt the disciples.  Jesus knew what would happen, but His men refused to accept the truth about their own weakness and His power.  Quoting from the Old Testament (Zechariah 13:7-8), Jesus predicted that none of the disciples would stay loyal to Him: they would all fall away.
 
Peter haughtily contradicted his Master.  Perhaps he could accept that the others were weak, and might well desert their Lord, but he was stronger than them.  Peter boasted that he would be utterly dependable.  Pride had risen up like a poisonous snake to strike at the truth of Jesus' words.  But Jesus persisted, with crushingly accurate detail, to tell Peter how weak he would be less than 12 hours later (Matthew 26:69-75).  Even so, Peter's self-important delusion (that he alone could support Jesus in His time of suffering) got the better of him, and led the others to repeat the same empty promise.
 
The arrogant fisherman could only see what he would do, in his own strength, for Jesus; and not what Jesus would do, in His own weakness and suffering, for Peter (1 Peter 1:18-19).  The promise of rising from death was ignored, along with the assurance that they would see Him again in Galilee. Jesus would not be left behind but would go ahead of them – a promise they forgot until reiterated by an angel outside the empty tomb (Mark 16:7).
 
The essence of sin is a refusal to accept God's Word as being fully true.  That was how Eve and Adam started their fall from grace (Genesis 3:1-7).  It is the same for us.  Our proud hearts are unwilling to believe the truth about ourselves, which is why we need God to tell us that we are systemically inclined to sin.  Despite our most sincere protests, we will all fail Him, others and ourselves.  The other truth that we often refuse to accept is that nothing defeats Jesus.  He is stopped by nothing, and even when we think He cannot act in power, we find Him going ahead of us to welcome and forgive us.  It is not what we can do for Him that counts … but what He has done, and is doing, for us.  Accept these two big truths and enjoy the godly adventure that is the life of faith, instead of a series of woeful spiritual defeats.