The Power of Concentration

The Power of Concentration is a classic psychology/self-help book by Theron Q. Dumont. This venerable psychology classic contains the following excerpt:
It is of the utmost value to learn how to concentrate. To make the greatest success of anything you must be able to concentrate your entire thought upon the idea you are working on. The person that is able to concentrate utilizes all constructive thoughts and shuts out all destructive ones. The greatest man would accomplish nothing if he lacked concentration.