Sonder (noun):
the feeling one has on realizing that every other individual one sees has a life as full and real as one’s own, in which they are the central character and others, including oneself, have secondary or insignificant roles:
In a state of sonder, each of us is at once a hero, a supporting cast member, and an extra in overlapping stories.
This one always makes me smile, because it's from the Dictionary of Obscure Sorrows. It's just some guy's blog in which he comes up with new words to express experiences and emotions that are difficult to describe, and that specific one has thoroughly broken containment