That each random passerby is living a life as vivid and complex as your own-populated with their own ambitions, friends, routines, worries and inherited craziness-an epic story that continues invisibly around you like an anthill sprawling deep underground, with elaborate passageways to thousands of other lives that you'll never know existed, in which you might appear only once, as an extra sipping coffee in the background, as a blur of traffic passing on the highway, as a lighted window at dusk.
Yeah, like the other commenter said, this is an incomplete sentence. Also, this definition was written by a group of people called "the dictonary of obscure sorrows"
That all of that what? Really, maybe it sounds cool starting this ramble with "That.." but you need to put a verb to it at some point. That each passerby does all that... is amazing, that each passerby does that... scares the crap out of me, that each passerby does that... is just how things are and not really noteworthy.