But much the commoner type of success in every walk of life and in every species of effort is that which comes to the man who differs from his fellows not by the kind of quality which he possesses but by the degree of development which he has given that quality.
 Theodore Roosevelt, Theodore Roosevelt; an Autobiography (1913). copy citation

Context

“Of course the proper performance of each implies much previous study or training, but in no one of them is success to be attained save by the altogether exceptional man who has in him the something additional which the ordinary man does not have. This is the most striking kind of success, and it can be attained only by the man who has in him the quality which separates him in kind no less than in degree from his fellows. But much the commoner type of success in every walk of life and in every species of effort is that which comes to the man who differs from his fellows not by the kind of quality which he possesses but by the degree of development which he has given that quality. This kind of success is open to a large number of persons, if only they seriously determine to achieve it. It is the kind of success which is open to the average man of sound body and fair mind, who has no remarkable mental or physical attributes, but who gets just as much as possible in the way of work out of the aptitudes that he does possess.” source