Lol, well since you're into MA now, you should know that conflict avoidance is actually the primary lesson of budo.
You'll enjoy Sun Tsu's Art of War, get a copy. He says a lot about conflict, perhaps the most relevant for you is that 'subdue the enemy without fighting is the supreme excellence'.
When you do have to fight, make sure you fight to win or don't bother. This is so you win not just that fight, but every other fight that would have come after. This goes for non-physical conflicts also. I don't think you would have been able to do that w/your ex, nor was it really necessary, so you did right.