The 80% Idea.

Speaking to Fast Company, Cofounder and Creative Director Masashi Kawamura of the ad agency Party, observed that a "great idea to pitch is one that's only 80% there. We love to have that 20 extra space. It's a good space."

Kawamura says the 100% idea in your head "only gets smaller from there."

That's a liberating way to think about creativity: that it doesn't have to arrive fully formed.