"You are more apt to “rust” out your brain from disuse than you are to wear it out from use."

http://tinyurl.com/4b3znpx

Unlike a mechanical device that eventually wears out and must be replaced if it is used continually and consistently, the mind grows only stronger when it is active. The more you exercise and stretch your brain, the more proficient it becomes. Disuse, however, will have the same effect upon your mind as it will upon a machine. The most intricate, most powerful machine in the world and the greatest minds will rust away unless they are used. Unless you manage your schedule to permit time for study and learning, it is easy to yield to the temptation to spend your free time in thoughtless, mind-numbing, escapist pastimes. Relaxation is important, but so is gaining new knowledge. Make sure your daily schedule includes an allotment of time for both.