All good things must come to an end.  A watched pot never boils.   Beggars can't be choosers.  Don't bite the hands that feed you.  Don't put too many irons in the fire.  If it ain't broken, don't fix it.  The pen is mightier than the sword.  Two heads are better than one.  Two wrongs don't make a right.  The enemy of my enemy is my friend.