“It is not the clear-sighted who lead the world. Great achievements are accomplished in a blessed, warm mental fog.”

Source: Aphorisms and Reflections (1901), p. 164

Source: Big Sur

Source: Drive: The Surprising Truth About What Motivates Us

Part II, chapter 5.
Proverbs (1546), Bartlett's Familiar Quotations, 10th ed. (1919)

Often abbreviated to: Nothing great in the World has been accomplished without passion.
Variant translation: We may affirm absolutely that nothing great in the world has ever been accomplished without enthusiasm.
Lectures on the Philosophy of History (1832), Volume 1
Variant: We may affirm absolutely that nothing great in the world has been accomplished without passion.
Context: We assert then that nothing has been accomplished without interest on the part of the actors; and — if interest be called passion, inasmuch as the whole individuality, to the neglect of all other actual or possible interests and claims, is devoted to an object with every fibre of volition, concentrating all its desires and powers upon it — we may affirm absolutely that nothing great in the World has been accomplished without passion.

Written in his prison diary
1940s