Walter's Alternate Daydreams
The text structure characterizes Walter Mitty as a timid, small, insignificant man through the use of daydreams.
First, Walter Mitty is a victim of the people around him. His wife treats him like a child, and the parking lot attendant and cop were rude to him.
Walter uses daydreams to escape his disrespected, boring life. instead of being treated like a child, he is a commander, a respected surgeon, and a potential lawbreaker.
Walter's daydreams give him confidence in the real world. When his wife was complaining about him, he was defending himself because of the daydreams giving him a sense of self respect.