The Difficulty of the Task Accelerates the Insight Process

Excerpt from Imagine: How Creativity Works by Jonah Lehrer: 

The constant need for insights has shaped the creative process. In fact, these radical breakthroughs are so valuable that we've invented traditions and rituals that increase the probability of an epiphany, making us more likely to hear those remote associations coming through the right hemisphere.

Just look at poets, who often rely on literary forms with strict requirements, such as haikus and sonnets. At first glance, this writing method makes little sense, since the creative act then becomes much more difficult. Instead of composing freely, poets frustrate themselves with structural constraints. 

But that's precisely the point. Unless poets are stumped by the form, unless they are forced to look beyond the obvious associations, they'll never invent and original line. They'll be stuck with clichés and conventions, with predictable adjectives and boring verbs. And this is why poetic forms are so important. When a poet needs to find a rhyming word with exactly three syllables or an adjective that fits the iambic scheme, he ends up uncovering all sorts of unexpected connections; the difficulty of the task accelerates the insight process. 

See also: "How to Cultivate Eureka Moments," a review of Imagine by Michiko Kakutani, The New York Times, April 2, 2012