He brought him to Jesus. Jesus looked at him, and said, "You are Simon the son of Jonah. You shall be called Cephas" (which is by interpretation, Peter).
It is not something that you can set your mind to and become. That is, "I am going to live this new dynamic life. I'm not going to walk in darkness any more; I'm going to live a generous, self-sacrificing life, the life that is the ideal that God has declared for man." You can't do it by the will of the flesh.