"The military has no constant form, just as water has no constant shape - adapt as you face the enemy, without letting them know beforehand what you are going to do."

Next Quote

It makes him contemptible to be considered fickle, frivolous, effeminate, mean-spirited, irresolute, from all of which a prince should guard himself as from a rock; and he should endeavour to show in his actions greatness, courage, gravity, and fortitude; and in his private dealings with his subjects let him show that his judgments are irrevocable, and maintain himself in such reputation that no one can hope either to deceive him or to get round him.

— Niccolo Machiavelli