It's what he needs to hear. He needs something to do, he's always better off with something to do. It's not an immediate action, but it's a reminder that they can't afford the luxury of emotional collapse.

(He's selfish, he thinks, making Cassian take the lead here--a man who died at the beginning of his own war, who had to wonder if what he'd done made a difference. Poe doesn't get to fall apart over the prospect when Cassian had to live with it for months.)

Poe grips Cassian's wrist lightly, a motion of solidarity.

"Hey, on the bright side, we won't have to wave at the cameras any more when we pee. Or was that just me?"