As a kid, we’re asked what we want to be when we grow up. We answer, doctor, firefighter, pilot, teacher, etc. People aspire to be important, reliable cogs in life who bring benefit to themselves and others.
The disciple Peter was no different. His time with Jesus led him to want to be a dedicated and reliable servant. In fact, he was sure he could be that person. But Jesus recognized Peter (like all of us) was prone to mistakes and protection of self.
We all must realize our human frailties and depend on Jesus to cover for us when we fail in life.