It was in the beginning of "us". He was always at his ex's beck and call because she had "issues". Funny how her issues always happened on our dates.

So one night, he calls and says, "I don't think i can hang out tonight...something came up." I said, "I will not be usurped by your ex. (ooh big word!) If you want to be with me, you cannot be your ex's knight in shining armour. She can make friends. This is not healthy. I value my time and now my night is shot."
He got upset and I told him, calmly, that i was not to be 2nd choice. I was 31 and grown and mature enough to see that he wasn't ready for any kind of real relationship. If he wanted to go save people, that was fine, but i wasn't going to wait around. I was calm, but heated!!!

He was trying to explain that he wasn't choosing her over me, blah blah blah, and I politely told him where to stick his delusions.
We didn't talk for 4 days. Then he showed up one evening, unannounced (thank god I looked good!) and said, "Ok, I'm ready."
While it wasn't a big argument, it was a very poignant moment in our relationship. I set a boundary and he never crossed it after that.
We don't really argue. We just don't. We both grew up with fighting parents and we swore we'd never do that. If something is heated, we'll take a break and write it out or talk about it calmly to resolve the issue after we've calmed down. But that doesn't happen often. I'm old. I like a drama-free life. I do not control him, he doesn't control me. I something gets effed up by one of us, oh well, it was a mistake. Apologize and fix it. Don't fight over it. Life is a learning path. No sense in getting angry about things.