Great works are performed not by strength, but perseverance
 Samuel Johnson, The History of Rasselas, Prince of Abissinia (1759). copy citation

Context

“The Prince for a moment appeared to be discouraged. “Sir,” said his companion, “practice will enable us to continue our labour for a longer time. Mark, however, how far we have advanced, and ye will find that our toil will some time have an end. Great works are performed not by strength, but perseverance; yonder palace was raised by single stones, yet you see its height and spaciousness. He that shall walk with vigour three hours a day, will pass in seven years a space equal to the circumference of the globe.”” source