How Charlie changes throughout the book

 I'm currently reading the Perks of Being a Wallflower. One thing I have been noticing is that throughout the book the main character, Charlie, undergoes major personality changes. In the beginning of the book, Charlie sits back and watches his life and the situations around him. As the book progresses, Charlie starts to participate more in his life. In my opinion this all happens after Bill, his high school English teacher, gives Charlie a talk about being a participater, not just an observer. At first Charlie is convinced he can't change that; it's simply the way he is. But soon enough Charlie proves himself wrong. He stands up to his bully by physically fighting back, and he tattles on his sister after observing a situation that he feels puts her in danger. After seeing the way Charlie could change in such a short period of time, it made me start to question my actions. Am I just an observer, or am I a participator in my life?