I first read the short story The Secret Life of Walter Mitty by James Thurber in high school. In his daydreams, Walter Mitty is a Navy commander flying through a terrible storm, a brilliant surgeon who saves the life of a millionaire banker, an expert marksman on trial for murder, and so on. His exciting imaginary adventures let him escape his boring existence and his nagging, controlling wife.
The 1947 movie version starring Danny Kaye expands the story a bit but is basically scripted along the same lines. I like the 2013 version starring Ben Stiller which changes the story much more.
Walter Mitty still wants to be a hero and have fantastic adventures, but his daydreams are inspired by his behind-the-scenes job developing photographs for Life magazine and by his desire to meet and date a coworker, Cheryl (Kristen Wiig). When a negative intended for the cover of the magazine is missing, Walter decides to go on a real life adventure to find its photographer Sean O'Connell (Sean Penn). He is forever changed from a dreamer into a man of action.
The part of the movie I enjoyed most is a brief scene in the Himalayas where Sean O'Connell is trying to photograph the elusive snow leopard. He and Walter see the "ghost cat," but he doesn't take any pictures. He says if he likes a moment and wants to stay in it, he doesn't want the camera to distract him. I agree that life is enriched by being present without the need to document and widely broadcast every special experience.