To get excited about something to the point of being fanatical and effusive, except only to be brought down to the harsh reality of truth, or factual information.
Person 1: "Dude, I just bought a brand new BMW 7 series!"
Person 2: "Uh, do you realize the maintanence, gas usage, and insurance costs of that? You can barely afford the monthly car payments."
** Person 1 has just been "bleeb'd."