A consideration of these characteristics of habits makes clear its dangers as well as its values. The fact that habit is based on actual changes which take place in the nervous system, that its foundation is physical, emphasizes its binding power. Most people in talking and thinking of habit regard it as something primarily mental in nature and therefore believe all that is necessary to break any habit is the sufficient exercise of will power. But will power, however strong, cannot break actual physical connections, and it is such connections that bind us to a certain line of activity instead of any other, when once the habit is formed. It is just as logical to expect a car which is started on its own track to suddenly go off on to another track where there is no switch, as to expect a nerve current traveling along its habitual conduction unit to run off on some other line of nervous discharge. Habit once formed binds that particular line of thought to action, either good or bad. Of course habits may be broken, but it is a work of time and must result from definite physical changes. Every habit formed lessens the likelihood of any other response coming in that particular situation. Every interest formed, every act of skill perfected, every method of work adopted, every principle or ideal accepted, limits the recognition of any other possible line of action in that situation. Habit binds to one particular response and at the same time blinds the individual to any other alternative. The danger of this is obvious. If the habits formed are bad or wasteful ones, the individual is handicapped in his growth until new ones can be formed. On the other hand, habit makes for limitation.