Fear of not receiving a letter from Hogwarts School of Witchcraft and Wizardry on one's eleventh birthday.

A study recently showed that many children believe in the magical world of Harry Potter created by J.K. Rowling and are, in fact, fearful of it not existing. This fear often manifests itself in the form of an act described in the book which would be the first contact with the magical world in question - receiving a letter from Hogwarts. The build up to the eleventh birthday can be a time of anxiety for children suffering from this phobia.

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.