"Habits, scientists say, emerge because the brain is constantly looking for ways to save effort. Left to its own devices, the brain will try to make almost any routine into a habit, because habits allow our minds to ramp down more often."
I really enjoy these daily snippets from Delanceyplace, where the owner snips parts of books he's read [I wish I could read as voraciously] and sends them out with a link to the book, should someone's interest be peeked. This is from a book explaining habits = yesterday's was about Kit Carson, mountain man. Look in the archives for quite a few other interesting snippets.