The journey that Santiago undergoes is difficult. He is lonely at times, and he faces terrible danger, brutality and loss. However, he wants to change and grow, so he has no choice other than to literally "follow his dream" as the book's subtitle suggests. Many situations in the book illustrate the theme of journeying.
The sheep that Santiago herds for two years through the Andalusian fields are themselves journeying. The big difference between the sheep and Santiago is that the sheep have given up their instincts. They depend entirely on the shepherd to lead them to food and water, whereas Santiago is motivated to think for himself as he proceeds on his journey. The sheep will get their food and water as long as a shepherd guides them. Santiago will get his treasure and discover his destiny, as long as he continues to develop his ability to think and find out for himself.
While Santiago is working in the crystal merchant's shop, Santiago's journey appears to end for a year. He thinks that when he earns enough money he will return to Spain. At the end of that year, however, he has undergone a certain amount of personal growth. At the last minute, he decides not to go back but to continue on his way toward reaching his dream. Perhaps his conviction to reach for his destiny is strengthened by witnessing the crystal merchant's reluctance to follow his own dream.