[He's a lot more jittery than he'd like to admit. Even though he's still dancing correctly, he has to intently focus on each individual step - or he'd be done before she (or anyone else in the room) could blink.
Most songs are long to Bart. Comes with the territory. This one, though? This one might've lasted an eternity. A beautiful, intensely sweet one where he's with the girl of his dreams... but still an eternity.]