How to not make your girlfriend feel good

Today after the WABC Father's Day Fight Against Prostate Cancer 5 mile race in Central Park, New York City:

Him: So how'd you do?
Me: Not too badly. I ran about nine and a half minute miles. I don't know though, it seems like I should be able to go faster than that.
Him: Yeah, I watched the eight minute milers and they don't look that different from you.
Me: Yeah, sometimes people pass me and I see them and think, I should be able to go that fast.
Him: Yeah, like this guy today. He was doing six minute miles, and he was in his sixties. And he was flying! And he only had one arm!
Me: [silent]