Many moons ago (probably around junior high school, I vaguely recall having read a story that really "pinged" on the "Walter Mitty" in me. (Hmmm...thinking about it again for the first time in too many years, I'd like to reread this story).
In a nutshell, the story, fictional or true, I have no idea (and also based on an old recollection which may have distorted some facts) related how a guy always rode the same bus or streetcar to and from work for years. Over time, he noticed many near collisions at a certain intersection that the ride passed, and he too played the "what if" game. He thought and thought about what he would do "WHEN" AND NOT "IF" the accident occurred. He relocated where he sat to have the better view and egress from his ride, noted where fire ext. was and probably made other preps as well.
One day his moment of heroism arrived, he ended up saving several folks and according to the bystanders, immediately jumped up before the ride stopped crashing and was running over to help the victims, presumably receiving kudos and commendations.