It seems likely that Peter’s usefulness for God was forged on that dark night of failure, when he finally realized what he was apart from Christ. Up to that point, Peter continued to try and be self-sufficient: “I can fix this! I can do this! Even if they all go, I’m your man!” But when Peter’s gaze met Christ’s and he realized the depths to which relying on his own strength had sunk him, then he was emptied in order that he might be filled; he was broken in order that he might be mended; he was brought to tears in order that he might know the joy of forgiveness.
Alister Begg, A Lesson on Running from Failure