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... Это и многое другое вы найдете в книге The Power of Concentration - Learn How to Concentrate (Q. Dumont Theron Q. Dumont)