Dean Winchester: Cas, you can’t… With everything that’s going on, you can’t just go dark like that. We didn’t know what happened to you. We were worried. That’s not okay.

Castiel: Well, I didn’t mean to add to your distress. I… Dean, I just keep failing. Again and again. When you were taken, I searched for months and I couldn’t find you. And then Kelly escaped on my watch, and I couldn’t find her. And I just wanted… I needed to come back here with a win for you. For myself.

From Supernatural – Season 12 Episode 19: ‘The Future’ (12×19) | TV series produced by The CW