Robert Collier 
The Law of the Higher Potential [EPUB ebook] 

Man’s principal business in life. The toil and worry, the wearisome grind and the back-breaking work, will go on in the future as in the past to those who will not use their minds. The less they use them, the more they will sweat. And the more they work only from the neck down, the less they will be paid and the more hopeless their lot will become. It is Mind that rules the world.