Peter’s answer at Caesarea Philippi is the most famous thing he ever says. Jesus blesses him for it and calls him the rock. Five verses later the same man tries to talk Jesus out of the cross and is told to get out of the way. Matthew does not soften either moment.
The Church begins its year with this Gospel on purpose. It is easy to imagine the Church as a building, or as the people who never put a foot wrong. Jesus builds it on a man who understood one thing perfectly and another thing not at all, and who would deny him within the year.
That leaves room for the rest of us. The question Jesus asks is still put to each person in turn: who do you say I am? Answering it is the first step. Letting him correct the rest of what we think is the work of a whole year, and this is the first Sunday of it.