“It seems to me that the natural world is the greatest source of excitement; the greatest source of visual beauty; the greatest source of intellectual interest. It is the greatest source of so much in life that makes life worth living.”
“Acceptance of the unacceptable is the greatest source of grace in this world.”
“The greatest happiness is to know the source of unhappiness.”
“...the greatest source of misery in the world, the greatest cause of anguish and hatred and sadness and death, was neither disease nor race nor religion. It was hope.”
“Today the greatest single source of wealth is between your ears.”
“Your most unhappy customers are your greatest source of learning.”