Arthur senses Eames is looking at him, so he opens his eyes to give Eames a flat look in return. "I was in the marines," he says. "I know what I'm talking about. Focus on your breathing. Count to seven in, then count to seven out."

It's clear he's just reiterating all the stuff he used to use to make it through the rougher nights in the military so there's not much command in his tone, just easy suggestion. When they were hunting vampires there were nights where they knew they might be woken up to fight off an attack, but they had to sleep anyway to make sure they were ready. He's speaking from experience.