What distraction jars Mitty out of his daydream?

In James Thurber's short story "The Secret Life of Walter Mitty," Walter Mitty is jolted out of his daydreams by his wife, who scolds him for being distracted and not paying attention while she is driving. This interruption pulls him back to reality, contrasting sharply with the adventurous fantasies he experiences in his mind. The mundane reality of his life often interrupts his vivid imagination, highlighting his struggles with conformity and escapism.