We read of Peter in the Gospel of John and he seems to be one of the most confident disciples among Jesus' followers.
Peter was the one who got out of the boat to walk on water with Jesus, believing that if Jesus could do it, then Jesus could help him do it as well... sure he sunk, but he was the only one bold enough to even try.
Peter was the first one who proclaimed that Jesus was the Messiah, he was confident in what he knew of Jesus's fulfillment of the prophecies and promises of God... what others thought of Jesus didn't really matter.
Peter was the one to admit that he wasn't worthy to have Jesus wash his feet at the Passover meal, because he had seen Jesus up close and personal. He had seen Jesus' holiness and he knew the issues in his own heart... I'm sure all the other disciples were thinking the same thing, but Peter was the one who spoke up.
Peter was the only one to move to defend Jesus when the soldiers came to arrest him because he knew Jesus was an innocent man... sure he would get reprimanded for working against God's plan, but he was willing to do something when everything seemed to be going so wrong.
Jesus makes it clear that His confidence was in God the Father, enabling Him to react calmly to those who came to arrest him - this was so different from Peter's bold act of violence. It was different because Peter's confidence was in his ability, his knowledge, his faith, his trust; rather than the one who gives the peace, the knowledge, and the confidence - God the Father.
What he needed and what I need is to place my confidence in God, who never fails; rather than in myself with all my limitations.