“common enemies make enemies become friends!”
“We share a common enemy, but does that make us friends?”
“If the enemy of my enemy is my friend, then a friend of my enemy, is my enemy.”
“We ought so to behave to one another as to avoid making enemies of our friends, and at the same time to make friends of our enemies.”
“Reveal not every secret you have to a friend, for how can you tell but that friend may hereafter become and enemy. And bring not all mischief you are able to upon an enemy, for he may one day become your friend.”
“To become the enemy, see yourself as the enemy of the enemy”