Being unconquerable lies with yourself; being conquerable lies with your enemy.
Rely not on the likelihood of the enemy's not coming, but on our own readiness to receive him
If you know neither the enemy nor yourself, you will succumb in every battle
Who can determine where one ends and the other begins?
If, however, you are indulgent, but unable to make your authority felt; kind-hearted, but unable to enforce your commands; and incapable, moreover, of quelling disorder: then your soldiers must be likened to spoilt children; they are useless for any practical purpose.
Making no mistakes is what establishes the certainty of victory, for it means conquering an enemy that is already defeated.