The Mind
Mind. A marvelous object. It shoots a thought a millisecond. Most of them don't make sense though. Directing them is where the real challenge lies. We all think without stopping. May be not even in sleep. But great thinkers are those who have learned the art of concentrating their thoughts on one thing. Once you have succeeded in doing that, the rest is relatively easy. It is in fact harder to come out that state of concentration. Take John Nash for instance.