For spiritual reading during Lent I've been using The Hour of Jesus in the Gospel of John by Ignace de la Potterie, SJ.
The passage concerning Peter's denials took on a new meaning for me. When the servant girl asks Peter if he was one of Jesus' disciples, he denies it. The word the Gospel uses for the servant girl means literally in Greek "gatekeeper."
Suddenly the irony of it all jumped right out. John uses a lot of irony, and here consider what's going on. Peter holds the keys to the kingdom of heaven. Jesus had commissioned him to do that. So Peter was the gatekeeper to heaven, or he would be eventually. That was the role he was destined for.
But he was afraid of a servant girl who was keeping the door to the palace of the high priest Annas. Peter cowered before this girl. John's Gospel speaks much of the theme of darkness. So we see it here: the kingdom of darkness taking over to the point where the one holding the keys to the kingdom of God quakes in fear before the one holding the keys to an earthly place. And out of fear, Peter denies the Lord.
And what about today? Doesn't this continually happen? As baptized Christians, we are filled with the Holy Spirit and the grace of God. Yet do we sometimes cower in fear before those who would ridicule our faith? But in the Spirit, we are stronger than the power of evil. The devil's greatest lie is to get us to believe that evil is stronger than good. It is not; it may gain the upper hand for a while but in the end, God will scatter the forces of darkness. Christ has already won the victory for us.