What characteristics does Walter Mitty wish he had in "The Secret Life of Walter Mitty"?

Walter Mitty would like to be assertive, commanding, courageous, brave, fearless, heroic, and unwavering.
"The Secret Life of Walter Mitty" is a darkly humorous tale of a man who is defeated by authority and audacity, and emasculated by an insensitive wife. Apparently consigned to conducting his domineering wife to town and running silly errands for her, Walter drives along pretending that he is the courageous Commander of a Navy hydroplane until reality interrupts. Then, he is reduced to what has been called the "hen-pecked" husband as his wife scolds the meek Walter and reminds him to buy overshoes and wear his gloves.
Shortly after dropping off his wife at the salon, Mitty drifts into another wishful daydream in which he is again a leader. This time he is a famous surgeon, who assertively fixes a faulty piston so that an operation can continue. In sharp contrast to this heroism and commanding persona, Mitty is reduced again by reality as a lowly parking-lot attendant shouts at him, "Back it up, Mac!" Then, Mitty becomes so nervous that he cannot maneuver the car correctly. Embarrassed, Mitty almost forgets to hand the youth the key; then, the attendant backs up the car with insolent skill that demeans poor Mitty.

"They're so cocky," thought Walter Mitty, walking along Main Street; "they think they know everything."

Mitty recalls how he was mocked by a garage-man who had to come out to take off the winter chains from the car because in his attempts to do so, Mitty had the chains wound around the axle. "...next time...I'll wear my right arm in a sling...." This compensatory plan leads to another daydream in Mitty: This time he is himself and he is on trial for murder. However, his shooting arm was in a sling on the night of the murder. Boldly, nevertheless, Mitty asserts, "I could have killed Gregory Fitzhurst at three hundred feet with my left hand." Chaos breaks out in the courtroom and a beautiful girl hugs Mitty. When the District Attorney strikes her "savagely," the fearless Mitty punches him on the chin, saying, "You miserable cur!"
In reality, the submissive Walter Mitty walks down the street and he remembers the second errand, "Puppy biscuit." A woman laughs as she passes him, saying to her companion, "He said 'puppy biscuit' to himself. Later, Walter Mitty walks to the hotel where is supposed to wait for his wife. In the lobby he sits in a large leather chair that faces the window. After having picked up a copy of a political and general interest magazine of the time named Liberty, a new daydream comes to him. This time he is a captain in World War I and heroically he is going to blow up the ammunition dump of the Germans. Pouring another brandy and "tossing it off" with much machismo, Captain Mitty straps on his huge Webley-Vickers automatic and sets out to destroy the enemy's ammunition. "Cheerio," the heroic Mitty shouts bravely.
This dream is interrupted by his returning wife, who immediately scolds him for sitting where she cannot see him. When she asks him why he hides, Walter Mitty tells her, "I was thinking....Does it ever occur to you that I am sometimes thinking?"

She looked at him. "I'm going to take your temperature when I get you home," she said.

Mitty makes no comment to her demeaning response to him. But, the doors seem to make a derisive sound as they depart the hotel. "Wait a minute," his wife commands him. "She was more than a minute." Walter Mitty lights a cigarette as it begins to rain. He leans against a wall with his shoulders back. "'To hell with the handkerchief,' said Walter Mitty scornfully" as he imagines himself facing a firing squad. All his hope for bravery and assertiveness dashed, Mitty is yet unwavering in his escape.