Jonah Lehrer has a good article in the New Yorker, The Eureka Hunt (pdf), looking at research on what happens inside our heads when we come up with sudden insights. It seems to suggest it's ok to try, but best not to try too much. Here's a snippet:

The insight process, as sketched by Jung-Beeman and Kounios, is a delicate mental balancing act. At first, the brain lavishes the scarce resource of attention on a single problem. But, once the brain is sufficiently focussed, the cortex needs to relax in order to seek out the more remote association in the right hemisphere, which will provide the insight. “The relaxation phase is crucial,” Jung-Beeman said. “That’s why so many in-sights happen during warm showers.” Another ideal moment for insights, according to the scientists, is the early morning, right after we wake up. The drowsy brain is unwound and disorganized, open to all sorts of unconventional ideas. The right hemisphere is also unusually active... We do some of our best thinking when we’re still half asleep...

(T)he insight process is an act of cognitive deliberation—the brain must be focussed on the task at hand—transformed by accidental, serendipitous connections. We must concentrate, but we must concentrate on letting the mind wander.

Hat tip: David Smith

UPDATE: I liked Earl's riff on this theme:

That's why the Christians begin the bible with "in the beginning there was nothing" rather than, "in the beginning there was a brainstroming session where nothing was too stupid to go on the table".