What did Brian’s English teacher talk about? How can this help him now?

From the text:

Brian had once had an English teacher, a guy named Perpich, who was always talking about being positive, thinking positive, staying on top of things. That's how Perpich had put it—stay positive and stay on top of things. Brian thought of him now— wondered how to stay positive and stay on top of this. All Perpich would say is that I have to get motivated. He was always telling kids to get motivated.

Brian's memory of Mr. Perpich's words helped to get him on track, access his situation, and concentrate on what he had, as opposed to what he didn't have.