People who say that so-and-so is "in a rut" and that something should be done about it are often the sort who will watch an ant working contentedly and then devise cunning obstructions to throw it off the track. Their idea that being in a rut is automatically terrible, either frustrating or deadening, is nonsense. There are good ruts and bad ones, and to an outsider they may look as alike as two pea-pods, but the person in the rut knows the difference. Those of us lucky enough to have fallen into the right rut-- compatible in shape, scenery, direction or lack of direction-- don't take kindly to change. In my own case, my surroundings and methods of working suit me so exactly that once when a prop was changed, the result was disastrous.

-- from "Pack Your Troubles and Sag"