Whenever I overhear my parents fighting, I immediately become very sad. I literally stop what I am doing until they stop, or until I can't hear them anymore. My behavior is pathetic, but it's still hard to control that response.
The best thing to do is to leave whenever they argue. Go to a friend's house, the park, the local 7-Eleven, etc. They'll eventually stop. If, however, you leave and they fight to the point at which one becomes seriously hurt, do not blame yourself for not being there. They are adults, and they are not your responsibility.
Nevertheless, try not to BAWW (cry) over their fighting, because self-pity gets people nowhere.