In "To Build a Fire", the man's reaction to the advice given to him by the "old-timer" demonstrates his foolishness and pride.
When the old-timer adviced the man not to venture out alone in the wilderness and to successfully build a fire in his first attempt, the man laughed and thought that needing a companion for the trail is "womanish". He believes that he can venture out on his own without needing any help; his foolish pride caused him his death.
