Dame Eleanor has a fascinating post and links to good articles about something called "decision fatigue." Put simply, researchers have found that your willpower goes down, as does your ability to make good decisions, when you've had to make a series of decisions over the course of a day. You'll do anything to make it stop, including compromising in ways that you don't want to do or refusing to make any decision at all. The effect is magnified if your brain is starved of glucose: it needs that energy for willpower, which is in keeping with what other brain researchers found earlier this year.
In personal terms, this makes a stunning amount of sense. All those chirpy self-help fillers in magazines and web sites urge us to "Try something different! Break up your routine! Take a new route home from work! Brush your teeth in a different direction!" as a route to creativity. But if you've ever tried those strategies, you realize that they're only for leisure times when you have no work to do, because they are exhausting.
Think about it. When you have to shop at a different grocery store, everything is in a different place and finding what you want among innumerable brands is tiring. Unless you have the fashion gene, which I do not, shopping for clothes is exhausting. Controlled novelty--going to the farmer's market or an art gallery--can be stimulating and get the creative juices flowing, but what allows creativity to survive on a daily basis is the certainty of a physical routine that lets your mind go free. Thoreau had this one right: "Simplify, simplify." So did William James on the value of habit. One person's controlled novelty might be another person's occasion for decision fatigue, but the principle is still there.
The recent Vanity Fair article on President Obama indicated that he's cut his wardrobe down to blue suits and gray suits, or something like that, so that he can cut down on the time spent deciding. Good call, Mr. President. Don't we do the same kinds of thing when we buy the same pair of pants or sweater in a couple of colors, just so we don't have to go to the department store again for a couple of years (or is that just my strategy)?
According to the researcher quoted in the New York Times article above, "people with the best self-control are the ones who structure their lives so as to conserve willpower. They don’t schedule endless back-to-back meetings. They avoid temptations like all-you-can-eat buffets, and they establish habits that eliminate the mental effort of making choices. Instead of deciding every morning whether or not to force themselves to exercise, they set up regular appointments to work out with a friend. Instead of counting on willpower to remain robust all day, they conserve it so that it’s available for emergencies and important decisions."
In other words, a regular routine isn't limiting to creativity. It's freeing because it conserves your energy to make the important decisions related to your creative life.