When I’m in writing mode for a novel, I get up at four a.m. and work for five to six hours. In the afternoon, I run for ten kilometers or swim for fifteen hundred meters (or do both), then I read a bit and listen to some music. I go to bed at nine p.m. I keep to this routine every day without variation. The repetition itself becomes the important thing; it’s a form of mesmerism. I mesmerize myself to reach a deeper state of mind. But to hold to such repetition for so long—six months to a year—requires a good amount of mental and physical strength. In that sense, writing a long novel is like survival training. Physical strength is as necessary as artistic sensitivity.
more from his interview, here, http://www.theparisreview.org/interviews/2/the-art-of-fiction-no-182-haruki-murakami