Do you pay special attention to what you're wearing when you know you'll be seeing an ex of your significant other?

Or have you run into them unexpectedly, and been happy you looked fab (or annoyed at the timing if you didn't)?

Personally, I'm more concerned about running into bf's colleague's wife, because she always looks effortlessly fantastic. But bf's ex (from years ago) and her wife are coming over in a few hours for a Homeland marathon, and I find myself wondering how to put together a lounge outfit that's casual-company appropriate.