In Life of Pi, there are numerous quotes that illustrate Pi's fear and his maturity. The entire novel is about Pi dealing with fear and in dealing, he becomes mature. You could even say he loses some (or most) of his innocence. Pi deals with his fear in two primary ways. First, he simply does what he has to do in order to survive. He takes responsibility for his own life. This is one of the hallmarks of maturity. Pi also uses daily rituals as if they were religious duties. This is why there is such a strong connection with surviving (life) and spirituality. But notice that when he begins to despair, or think he might die, those rituals and the spiritual connection fade as well and they can only be reinvigorated when Pi deals with his fear.
In Chapter 52, Pi takes an inventory. This is the real beginning of dealing with the situation (fear) and taking responsibility. Here, we also see the conflation of religion and survival. And remember that Pi is interested in science and religion. Consider that survival is the science of life and that religion is one way to give life meaning by framing it within a larger narrative: the religious/scientific connection is represented.
At the end of his list in Chapter 52, Pi lists, "1 boy with a complete set of light clothing but for one lost shoe/1 spotted hyena/1 Bengal tiger/1 lifeboat/1 ocean/1 God." Pi is being very practical here after dealing with the horrifying death of Orange Juice, making the list to see what his assets and liabilities are. By ending with God, Pi ends the list with the optimistic note that no matter how scared he may be and no matter how hopeless the situation may become, he will never be alone. Furthermore, with 1 God, there is the sense that, despite the horrible circumstances, God works in mysterious ways. Many religions develop around stories, narratives which explain God's plan or why things in life occur the way they do. Pi does this very thing with his time on the boat. He writes his own story with the thought that there must be a higher reason for the changes that he must undergo, a higher reason which he does not yet understand. He was a vegetarian but became a carnivore in order to survive. Although he is a vegetarian because of his principles, this is an example where Pi must be willing to change in order to live. He overcomes fear of changing. Change is obviously the necessary element of becoming mature.
Chapter 60 is short but it contains a clear shift where Pi is fearful to the point of utter despair, followed by a reinvigorating urge to live. "I saw my suffering for what it was, finite and insignificant, and I was still." After sleeping on it, Pi awoke in protest of this acceptance. "No! No! No! My suffering doesmatter. I want to live! I can't help but mix my life with that of the universe."
Here, Pi gives meaning to his suffering with respect to his own life and with respect to the much larger scheme of the universe. Again, Pi discusses religion prior to this revelation. By giving meaning to his suffering (and his life), Pi is able to deal with his fear. In this back and forth struggle of learning to understand how to survive, and what it all means, Pi matures by teaching himself about life, religion, suffering, triumph, and meaning. The more he learns, the more he is able to deal with fear.