Funny how we come up with strange expressions. Babies can be colicky, experience teething discomfort or suffer from any number of other minor ailments that do not allow them to sleep so well. Still, most people use the expression "sleep like a baby" to mean "get a restful sleep."

The sleep of a laboring man is sweet. Our bodies do tend to slip into a natural state of recuperation after we have tired them out. Bodily exercise, good eating habits and an eye to regular hours (sometimes known as routine) give us the conditions under which we function the best. Peace of mind is the other ingredient that allows us to "sleep like a baby."