There's an old Heinlein quip that, when arguing with your wife, if you find that you are wrong, apologize, and if you find that you're right, apologize. Take out the sexism, and it's still a good rule. It's particularly important to apologize when I least want to, because that's usually when I'm being a jerk. So here's the rule:
Apologize. It'll only hurt for a minute.
I suppose it's worth noting again that I've made these rules for myself because they're things I'm not good at.
There's a corollary to this rule:
Let the other guy go first; it's good for you.