Dean drinks to blot out the dreams, but the dreams come anyway.

Cas is always there; the trick is telling the real Castiel from the one Dean's subconscious creates. Usually it's not too hard to tell them apart, but occasionally Dean wakes up reaching for warm sea blue, and he'll wonder.

Then Cas will show up and get too close, watching Dean so wide open and intent that Dean can feel his own uncertainty choking him.

Cas never says anything, never even hints, and eventually Dean learns to ignore it all, especially the way his relief almost tastes like regret.