One way in which Brian's thoughts, feelings, and reactions change him is in his development of "tough hope."

When Brian is initially confronted with landing the aircraft, his thoughts center on how he is "gonna die." As he struggles to make sense of where he is and what he should do, Brian lacks the mental stamina to endure the perils of the wilderness. Brian's thoughts, feelings, and reactions help him develop a sense of internal strength, though. Brian begins this process by recalling the words of his teacher, Mr. Perpich, who would remind his students to approach challenges incrementally and that their own self-worth can help them face any situation bravely. From here, Brian develops a will to survive. For example, his reaction to the porcupine entering his shelter is to throw the hatchet against the wall, whereby sparks develop. From this, Brian learns how to make a fire. His experiences with needing to find food sources help him create different spears and weapons that he can use to hunt food. Brian emerges as a tower of mental fortitude in the way he deals with the tornado and moose attack. In each experience, Brian's thoughts, feelings, and reactions are geared towards surviving and enduring difficult times.

Over the course of the narrative, Brian develops a "tough hope," which demonstrates his commitment to survive the wilderness. His thoughts, feelings, and reactions show an unwillingness to be defeated:

He could feel new hope building in him. Not hope that he would be rescued—that was gone. But hope in his knowledge. Hope in the fact that he could learn and survive and take care of himself. Tough hope, he thought that night. I am full of tough hope.

Brian's "tough hope" transcends being rescued. It displays a resolve that he will survive. It represents how Brian's thoughts, feelings, and reactions have changed him.

In Hatchet, how did Brian's relationship with nature change?

Gary Paulsen's Hatchet is one of the great survival stories in literary history, and arguably the most famous featuring a young adult protagonist. The novel tells the story of 13-year-old Brian Robeson, who is on a flight to northern Canada when his plane crashes down, forcing him to survive for 54 days in the Canadian wilderness with nothing but a hatchet. 

This type of literary conflict is classically referred to as "Man vs. Wild," distinguished from the other standard conflicts of "Man vs. Man," "Man vs. Society," and "Man vs. Self." In some ways, this is the simplest type of conflict; a hero tries to survive amidst a chaotic and unfeeling natural world that has the potential to kill them. 

Hatchet follows familiar plot points in this world. First, the hero adjusts to his completely alien environment (Brian takes in the utter and total silence of the woods, something that never existed back home). Next, the wilderness begins to throw challenges at the hero as they struggle to achieve their basic needs for water, food, and shelter. After some embarrassing and/or painful mishaps, the hero begins to learn the lay of the land and achieve calm mastery over their environment. 

Though Brian is in the woods for less than two months, his mastery is undeniable as he successfully creates shelter, hunts small animals, makes fire, etc., strengthened by the fact that he goes on to star in four more novels with similar settings. And as he learns to navigate the "Wild," we see his relationship move from fear to respect, from fumbling to grace, and from anxiety to calmness. Their is a spiritual transformation that often takes place in any "Man vs. Wild" narrative, in which the hero comes to inadvertently love the land that he battles, and to create victory through symbiosis.