Hope

"Let no one be discouraged by the belief there is nothing one man or one woman can do against the enormous array of the world's ills - against misery and ignorance, injustice and violence... Few will have the greatness to bend history itself; but each of us can work to change a small portion of events, and in the total of all those acts will be written the history of this generation...
It is from the numberless diverse acts of courage and belief that human history is shaped. Each time a man stands up for an ideal, or acts to improve the lot of others, or strikes out against injustice, he sends a tiny ripple of hope, and crossing each other from a million different centers of energy and daring, those ripples build a current which can sweep down the mightiest walls of oppression and resistance."

Robert Kennedy, cited by Jeffrey Sachs in "The end of poverty, economic possibilities for our time", chapter "Our generation's challenge".
Jeffrey Sachs then concludes his book:

"Let the future say of our generation that we sent forth mighty currents of hope, and that we worked together to heal the world."