How does a lesson the Alchemist taught Santiago save his life?

Early in the novel The Alchemist, the titular character tells Santiago that "When you possess great treasures within you, and try to tell others of them, seldom are you believed." This simple statement saves Santiago's life, because toward the end of the novel he finally realizes the importance of having faith in destiny, instead of cursing it.
Santiago, a shepherd boy, curses his lot in life. He wanted to be rich. He learns that destiny has a plan for everyone and that he should have faith and embrace his destiny. Even though he ends up gaining money by the end of the novel, he realizes that what makes him rich is not the money, but instead the journey and the adventure that he took. Once he realizes the meaning of the alchemist's words, he is saved. His life is saved from a lifetime of disappointment.