"The necessity for struggle is one of the clever devices through which nature forces individuals to expand, develop, progress, and become strong through resistance. . .We are forced to recognize that this great universal necessity for struggle must have a definite and useful purpose. That purpose is to force the individual to sharpen his wits, arouse his enthusiasm, build up his spirit of faith, gain definiteness of purpose, develop his power of will, and inspire his faculty of imagination to give him new uses for old ideas and concepts. . ."

Source: Napoleon Hill (2013). “The Law of Success”, p.223, Courier Corporation