Imagination
Walter Mitty is a hapless daydreamer, and the "secret life" of the title refers to the fact that, in moments of boredom or dissatisfaction, Walter imagines an idealized version of his life. In this imagined reality, he is a superhero, a witty conversationalist, and a fierce adversary to despicable foes like Ted Hendrix.
As we learn throughout the movie, Walter uses his imagination to escape from the doldrums of life and find a sense of adventure that is missing in a colorless existence. His imagination is a good thing in that it is a source of stimulation, but it also takes him out of the present moment, and causes him to space out in the presence of loved ones. His imagination is at once a blessing and a curse.
Corporate Life
Walter works at Life Magazine, as a negatives assets manager. It is the corporate, faceless, and stereotypically boring part of the work that goes on at the magazine. While the photojournalist with whom he is most in contact lives a high-risk and exciting life traveling around the world and snapping beautiful photographs, Walter works in a dark office with Hernando, sorting through negatives and harboring a painfully unexpressed crush on a coworker. The film tries to portray the stultifying effects of corporate life, and the ways it makes people feel devalued in their labor. By the end of the film, however, when we see Sean O'Connell's cover tribute to the people who make the magazine, we see that the unsung heroes of the office are finally celebrated for the work they do.
Adventure
When Walter was younger, he was a much more adventurous person. As a teenager, he had a mohawk, rode a skateboard, and had dreams of traveling around the world. His father's death caused him to have to get a job and cut some of those adventurous ambitions short. Hence, he has found himself in a somewhat lackluster and frustrated existence in adulthood. As the story unfolds and Walter must go in search of the missing negative from Sean O'Connell, he begins to rekindle his own sense of adventure, taking risks he never thought he could take. Throughout the course of his travels, he jumps onto a helicopter, narrowly escapes the jaws of a shark, skateboards towards an erupting volcano, and climbs the Himalayas. The main arc of the film follows Walter's journey reconnecting with his own adventurous side.
Love
The film begins with Walter trying to work up the nerve to express his feelings to his coworker on a dating website. Walter loves Cheryl Melhoff, but is too scared to tell her so. He daydreams about sweeping her off her feet, but cannot muster the courage to strike up a conversation with her. As he embarks on the journey to find the missing negative, he enlists Cheryl's help and they begin to get to know each other. Slowly, he bridges his fantasy world with his reality and opens himself up to Cheryl. By the end of the film, they have started to kindle a romance, and the end of the film shows Cheryl and Walter holding hands as they walk down the street.
Accidents and Coincidences
For all Walter's adventurous and risk-taking moves, problems are usually solved by happy accidents, both revolving around Walter's mother. Walter realized that Sean visited his mother when he looks at the curve of her piano and compares it to a photo Sean took. Then later, when he thinks he lost negative 25, his mother presents him with the wallet he had tossed into the trash.
Additionally, Walter climbs the Himalayas alone, with no idea where Sean O'Connell is, and then miraculously runs into the photographer on his hike—a completely coincidental encounter. The film suggests that, as much as life is about taking big risks and being brave, it's also about happy accidents and coincidences.
Loss
As we learn towards the end of the film, a major reason that Walter turned towards work and safety rather than taking more risks in his life is that his father died when he was 17. This was not only devastating for Walter because his father was such a cheerleader of his, but it also meant that Walter needed to get a job and assume more responsibility in his family. Loss is at the center of Walter's tendency to play it safe, his sense that he needs to make the responsible and conservative choice.
Self Expression
Walter's journey in the film is not only about learning how to be braver and take more risks, like climbing mountains and jumping out of helicopters, but also about disclosing more about his inner life to the people around him. As mentioned before, Walter's tendency to drift into a dream world often cause him to space out and pull away from the people around him. As the movie progresses and he learns to open up to new experiences, he also learns to open up and express himself more. His ability to be honest helps him to build a relationship with Cheryl and others, and learn to speak up for himself.
