You mean that very first moment when truth shatters the pink glass you were looking through? It's like all the colors get sucked away; all what you believed is true just gets drained out of you, leaving an empty shell. While everyone around you remains the same, you are not anymore. No joy, nothing can cheer you up; just emptyness.
If you want to hear a more scientific approach: it's similar to the symptoms you have to experience after the death of a beloved relative. Despair, anger,... and finally acceptance.