What did you learn about Brian from his dreams and memories in Hatchet by Gary Paulsen?

From Brian’s dreams and memories, we learn he is overwhelmed with guilt about his mother’s affair.

Brian does not fully understand what is happening to his family. It is difficult to comprehend why his mother would have an affair. He just knows it is a secret and it is tearing him apart. The secret is so traumatic to him that, despite being stranded in the wilderness, he keeps dwelling on it. 

No, not secrets so much as just the Secret. What he knew and had not told anybody, what he knew about his mother that had caused the divorce, what he knew, what he knew — the Secret (Chapter 1). 

Brian often dreams of his mother and the Secret. He saw his mother kissing a blond man who was not his father. It is because of this that his parents are getting divorced. He does not tell them what he knows. 

Brian has vivid, recurring flashbacks of these memories. He was at the mall on his bike with his friend Terry. He saw his mother and a strange man in a car. 

Brian remembered everything in incredible detail. Remembered the time on the bank clock in the mall, flashing 3:31, then the temperature, 82, and the date. All the numbers were part of the memory, all of his life was part of the memory (Chapter 4). 

Although Brian has important things about which to worry, such as how to keep himself alive, he keeps coming back to this memory. Brian feels guilt for having seen it, and for not telling anyone he saw it. When he left his mother, he was not even really able to talk to her. She gave him the hatchet, he got on the plane, and that was it. The entire incident was very awkward for both of them.