He was thinking alone, and seriously racking his brain to find a direction for this single force four times multiplied, with which he did not doubt, as with the lever for which Archimedes sought, they should succeed in moving the world, when some one tapped gently at his door.
A person who doubts himself is like a man who would enlist in the ranks of his enemies and bear arms against himself. He makes his failure certain by himself being the first person to be convinced of it.
Happiness is like those palaces in fairy tales whose gates are guarded by dragons: we must fight in order to conquer it.