If you know the enemy and know yourself then you need not fear the result of a hundred battles. If you know yourself but not the enemy then every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle.
Quote by Sun Tzu (Chinese General)

The general who advances without coveting fame and retreats without fearing disgrace, whose only thought is to protect his country and do good service for his sovereign, is the jewel of the kingdom. -Sun Tzu