Walter Mitty can barely get through the day carrying out the trivial assignments that his overbearing wife provides for him. He appears to be incompetent at everything he tries: He is a poor driver, he is not at all handy (ex: his problems trying to change his snow chains), and he is so forgetful that he has to be constantly reminded what to do next. He is a man who has allowed his wife to dominate him in every way: She speaks to him as a person would speak to a child; she scolds and nags him constantly; and she has him wait on her like a servant. He has no job; he must be retired, but one wonders what kind of job he could have maintained long enough to reach retirement age. Quite opposite the heroes of which he constantly daydreams, Walter never stands up to his wife or for himself. Instead, he follows her commands in a subserviant manner, without question and in a dreamy state that almost suggests mental deterioration or instability. When he reminds his wife that he may have other things on his mind and asks her,
"Does it ever occur to you that I am sometimes thinking?"
she stares at him, telling him that "I'm going to take your temperature when I get you home..."
Walter is a milquetoast little man--a dreamer who is incapable of making decisions for himself, and probably lucky that his wife is still willing to take care of him. Like many people whose daydreams take them to worlds in which they never have the courage to explore in real life, Walter's only chance of ever doing anything remotely heroic is in his imagination.
Put very simply, Walter Mitty is scared to take any action beyond those accepted by society. He doesn't want to speak up when confronted, in case he will be challenged, and since he has no experience in his real life with challenge, he wouldn't know how to react. He can't even stand up to his wife, who treats him almost like a child; instead, he simply does what she tells him without protest:
In a way he hated these weekly trips to town -- he was always getting something wrong... But she would remember it. "Where's the what's-its- name?" she would ask. "Don't tell me you forgot the what's-its-name."
(Thurber, "The Secret Life of Walter Mitty," bnrg.cs.berkeley.edu)
There is no sense of what sort of man Mitty was in his youth; he seems to have succeeded at his job long enough to retire, but has no ambition for the future. He doesn't want to risk losing the mental comfort of a familiar life, and so he escapes to his imagination. In reality, it is unlikely that Mitty could ever work up the courage to become heroic; he simply doesn't have the mental acuity or physical skills.
The 1947 film subverts this, however, and shows Mitty growing as a person and finally confronting the negative influences in his life.
In real life James Thurber, the author of "The Secret Life of Walter Mitty," was badly handicapped because a childhood accident had made him partially blind. In his old age he became totally blind. He was always dependent upon others to a certain extent. The kinds of activities Walter Mitty fantasized about doing would have been impossible for Thurber, although he must have had similar fantasies himself. He was undoubtedly dependent upon his wife and resented that dependency. One of his favorite themes in both his stories and his cartoons was what he called "the war between men and women."
In spite of his serious handicap, Thurber became a highly successful writer and was generally regarded as America's best-loved humorist. He was associated with The New Yorker magazine as a staff writer, a contributor of stories and essays, and a cartoonist from its inception in the 1920s and wrote about his recollections of that peak period in The Years with Ross. "The Secret Life of Walter Mitty" is Thurber's most often anthologized story, but it only provides a glimpse of the wonderful works of this great American humorist.
Mitty's circumstances make it very unlikely that he could be the hero he wants to be. He is an older man who is starting to have difficulty performing certain tasks, so it is probably too late for him to become a Naval commander, an expert shooter, or a surgeon. Also, the situations in his real life do not call upon him to be brave or bold; for example, Mitty does not have the exceptional courage to buy the correct kind of puppy biscuits or to drive his wife to the hairdresser.