Take up my cross and follow Jesus.

Matthew 16:13-28
Simon Peter answered, “You are the Messiah, the Son of the living God.
Blessed are you, Simon son of Jonah, for this was not revealed to you by flesh and blood, but by my Father in heaven.
And I tell you that you are Peter,and on this rock I will build my church, and the gates of Hades will not overcome it. I will give you the keys of the kingdom of heaven; whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven.
Jesus turned and said to Peter, “Get behind me, Satan! You are a stumbling block to me; you do not have in mind the concerns of God, but merely human concerns.
Jesus beginning to prepare his disciples for the suffering that lies ahead.
But the recent promise has gone to Peter's head. The rock becomes an obstacle. God's spokesman turns devil's advocate.
Whoever wants to be my disciple must deny themselves and take up their cross and follow me.
Why?
Peter has the vision of heaven and from the flesh both. Peter is blessed for he followed Jesus way after Jesus was risen. 
Peter is the rock, and he hold the key of the kingdom of heaven.
Jesus is the Messiah, the Son of the living God, this is the real identity of the Jesus Christ.
Simon speaks for all the apostles in asserting his belief that Jesus is the Messiah. And Jesus sees in him the man of rock he will become after the shattering experience of denial and forgiveness.
It is Peter, the natural spokesman, who will be responsible more than any other for the formation of the church at Pentecost.
The authority given to Peter is given equally to the others. The idea of the keys echos Isaiah 22:22. God is no bound by whatever Peter may say. But anything done by the disciple in accordance with Christ's will is to have permanent validity.
How?
Take up my cross and follow Jesus.