With the introduction of his Grace back into the equation, Castiel already feels braver. Feels like he can succeed, really begin to actually redeem himself, and with every Leviathan they kill, Castiel will become more capable of protecting Sam and Dean.

It's doable. Hell, it's downright possible.

Castiel heads outside and stays there for nearly fifteen minutes with Sam. When he returns, he opens the door just widely enough to poke his head inside. "Dean. We're ready to go."