If Castiel knew about the fear and the frustration he'd feel worse, if that were even possible. Looking at his old companion now all he feels is guilt, crippling guilt, and another feeling he can't quite explain.

When the silence grows too uncomfortable, Castiel sweeps his hand across the back of his neck where hair is still standing on end. "I should go." This was inappropriate, and Balthazar seeming much more acclimated was clearly here first. There's no reason for him to make things worse for him.