It becomes the urgent duty of ...
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Effort only fully releases its reward after a person refuses to quit.
Never complain and never explain.
A good plan violently executed now is better than a perfect plan executed next week.
George S. Patton
Problems are not stop signs, they are guidelines.
Robert Schuller
Never give up, for that is just the place and time that the tide will turn.
Harriet Beecher Stowe
Quotes from the same author
With an absurd oversimplification, the "invention" of calculus [method in mathematics] is sometimes ascribed to two men, Newton and Leibniz.
Richard Courant
With an absurd oversimplification, the 'invention' of the calculus is sometimes ascribed to two men, Newton and Leibniz. In reality, the calculus is the product of a long evolution that was neither initiated nor terminated by Newton and Leibniz, but in which both played a decisive part.
Richard Courant