Arthur wasn't nervous.
Why would he be? It was just dinner, drinks, with Ariadne. He'd been CIA, he'd broken into people's minds to steal information, he'd been shot more times than he cared to remember. What was a meal compared to all of that?
Right. So he re-tightened the tie he'd considered (more than once) taking off and smoothed his collar down with absent fingers. And a minute later when he decided that no, he would take it off, and the vest too, Arthur gave himself the mental kick he needed by asking himself just what Eames would make of him right then. That got him out the door--neat tie, immaculate vest and all.
It was six twenty-five when he pressed the buzzer to Ariadne's apartment. Arthur tugged at the bottom front of his vest once before pushing his hands into his pockets and looking around the street as he waited.