The author of the book uses the cold and desolate setting and the man who continuously makes careless decisions as examples to prove his argument that individuals overestimate their abilities and limits.
At the start of the story the man underestimates the conditions of nature and travels all by himself in these conditions. The conditions are 50 degrees below zero meaning they are life threatening.
The man overestimated himself when crossing the frozen river and ended up falling in even after he had already sent his dog over to check and watched the dog fall in before him.
In order for the man to survive he had to build a fire for warmth however he underestimated the power of nature and a large chunk of snow fell onto his fire and put it out.