After Peter's dramatic confession of the identity of Jesus, perhaps he expected a triumphant procession to start.  But even before the transfiguration (Mark 9:2-10), Jesus has to teach the apostles that He was to be the Christ who suffered.  To be glorified, yes … eventually: but to suffer was the first essential.  That had been prophesied about Jesus (Isaiah 53:1-12); it was the pattern of the Old Testament prophets (Matthew 5:11-12; Matthew 23:35) and would be the life-expectation of the apostles (John 15:18-21).  They needed to be prepared.

But Peter was so angry that Jesus might even contemplate suffering that he dared to rebuke Jesus!  His mind was so fixed on the power and the glory, that he could not see the necessity for the cross.  But Peter was not in charge.  Jesus looked up from the private correction that Peter tried to administer, and rebuked Peter so severely that he would never forget it.  Jesus exposed Peter's thinking as not only fleshly and worldly, but also devilish.  Satan tried to use the apostle's mouth to deflect Jesus from His course (differently, Judas' mouth was used to betray Jesus, and confirm the betrayal with a kiss).  Peter's ambition was for Jesus to become the popular rebel leader who would overthrow the Romans.  Jesus' ambition was to die as a sacrifice for the sins of the world (1 John 2:2).  The two motivations, desires, ways to proceed and objectives were utterly opposed.  Peter's way showed the evil side of humanity; Jesus' way was God’s plan.  

Suffering as a Christian is partly due to the hatred of the ungodly against the godly, and partly the will of God to demonstrate the radical difference of a Christ-like church.  Paul taught this plainly in Philippians 1:27-29.  But the principal reason for Christ's suffering was to take away the sins of the world (John 1:29) - opening the way for forgiveness, adoption into God's family and an eternal inheritance for all who repent and believe the gospel (Hebrews 9:28).  Nobody understood that before the resurrection and Pentecost: neither disciples, the band of female supporters, religious antagonists nor the Roman authorities (1 Corinthians 2:7-9).  The full meaning only became clear at Pentecost when the Holy Spirit put the pieces of the jigsaw together (1 Corinthians 2:10).  

The world cannot see the point of the suffering of Jesus, or the suffering of the church; but when someone does, it is life-changing!  And yet the church so often refuses to announce the Saviour and heaven-opener, the only way to Father God.  So to talk about Jesus as the kind teacher, or the powerful healer, is to miss the point.  Jesus was so called, because he would 'save His people from their sins' (Matthew 1:21).  And that meant the cross.  Omit that in your conversation, and Satan has won another battle.  Is this a much-needed rebuke to us also?