"Treat your friend as if he might become an enemy."
"Use your enemy's hand to catch a snake. "
"We can learn even from our enemies. "
"Always forgive your enemies; nothing annoys them so much. "
"Never interrupt your enemy when he is making a mistake."
"If you want to make peace; you don't talk to your friends. You talk to your enemies. "
"Forgive your enemies; but never forget their names."
"Never explain--your friends do not need it and your enemies will not believe you anyway."
"He hasn't an enemy in the world - but all his friends hate him."
"A wise man gets more use from his enemies than a fool from his friends."