When Sam runs away from home to live on the mountain, he is setting out to be alone. There were too many people living in his house in New York, with Sam's parents raising and feeding eight children (besides Sam). Sam initially enjoys his solitude.
Sam goes to great lengths to avoid contact with other people during his year in the wilderness, but he does make several human friends.
As the story goes on Sam changes from being happy alone on the mountain to craving more human contact. This is one of the most significant changes he goes through. In the end, Sam is still torn about the merits of building a real, family house in the woods, but he is glad to have the companionship of his family.
Other changes take place for Sam as he learns to overcome certain fears in the woods.
When winter arrived he had plenty of supplies, but he was still scared.
Sam's fears of having too little firewood and of being trapped in his tree by the snow prove to be rather easily overcome. Sam's confidence grows through the winter after he has faced his winter fears and conquered them.