From "Optimism: An Essay" (1903) by Helen Keller:
I, too, can work, and because I love to labor with my head and my hands, I am an optimist in spite of all. I used to think I should be thwarted in my desire to do something useful. But I have found out that though the ways in which I can make myself useful are few, yet the work open to me is endless. The gladdest laborer in the vineyard may be a cripple. Even should the others outstrip him, yet the vineyard ripens in the sun each year, and the full clusters weigh into his hand. Darwin could work only half an hour at a time; yet in many diligent half-hours he laid anew the foundations of philosophy. I long to accomplish a great and noble task; but it is my chief duty and joy to accomplish humble tasks as though they were great and noble. It is my service to think how I can best fulfil the demands that each day makes upon me, and to rejoice that others can do what I cannot. Green, the historian, tells us that the world is moved along, not only by the mighty shoves of its heroes, but also by the aggregate of the tiny pushes of each honest worker; and that thought alone suffices to guide me in this dark world and wide. I love the good that others do; for their activity is an assurance that whether I can help or not, the true and the good will stand sure.