A few weeks ago during sex with my girlfriend:
She: "You tired yet?"
Me: "A little..."
She: "That's too bad."
Me: "Aw, why?"
She: "I'm not."
Me: "Haha, are you serious?"
She: "Mmhmm."
Me: "Then I'm not tired either."
She: "Heehee, viagra's got nothing on me!"
I love my girlfriend.