When you wake up from a long, tense, complicated, plot-heavy dream, your heart racing, and for a half second you think -- "I have *got* to make notes on this; it would make a great novel." And then you wake up the rest of the way and realize nobody wants to read a novel about frantically packing for a flight.*
* Okay, maybe Nabokov or Nicholson Baker could make that novel actually interesting. Maybe.