This is the
defining moment in the story,
joke, lecture, etc. that you have been trying to work into the
conversation for hours at which you realize that all of your hard work, your intricate details, your subtle
explanations, are coming together to form one giant tangled mass of words that lead your
audience steadily away from anything resembling a
point.
You have many options in this situation. You can:
a) Stop your story immediately and admit that you are an incoherent fool.
b) Keep talking, eventually causing everyone to leave the room as your point becomes more and more distant.
c) Make up something interesting that is completely untrue (my personal favorite).
d) Run.