what is thensignificance of santiago becoming a sheperd rather than a priest,as his parents had hoped?why has he made this choice?what does being a shepard allow him to do

Being a shepard allows him not to be alone, but also live in peace. He being a priest will cause him to have emotions brew inside him more than often. Also, he does not want to do as his father says. He wants to do the things he is interested in, not what his father or mother are wanting him to do. He wants his own desires not theirs.