Quote 4
"They wanted me to be a priest, but I decided to become a shepherd." (1.85)
By defying his parents, Santiago is showing that he is not one of the sheep-like people who just do what people expect of him. He's already taken a first step toward taking control of his own life, by following his dream to travel. (Also, Brain Snack: Jesus is often symbolically referred to as a shepherd, and priests have "flocks," so … good job escaping your destiny, Santiago. Not.)
Quote 5
"You will never be able to escape from your heart. So it's better to listen to what it has to say. That way, you'll never have to fear an unanticipated blow." (2.508)
Santiago realizes that his heart is a little bit of a waffler. Half of the time it tells him it wants the treasure, but the other half of the time it's all boohoo and sob story. He learns that the more he listens to his heart and notices its changing emotions, the better prepared he'll be for sudden desires—because they won't be sudden.
Quote 6
"I have watched the caravan as it crossed the desert," he said. "The caravan and the desert speak the same language, and it's for that reason that the desert allows the crossing. It's going to test the caravan's every step to see if it's in time, and, if it is, we will make it to the oasis." (2.169)
Here, Santiago personifies the desert, talking about it as though it's a sentient being with the power to observe and also to react to what it observes, taking a part in writing history. Um, creepy much? We don't really want our deserts to be sentient; they're deadly enough as it is.