Castiel didn't want to sit. He wanted to turn invisible, or fly away, or sink through the ground, hide under the table--anything not to have to look right at Dean.

So he sunk down slowly into the chair like it was going to eat him, feeling the misery rising off Dean and knowing full well that he'd put it there. Dean was hurting. Dean was hurting because Castiel had let Lucifer do those things to him. He could have thrown him out, they'd have never have defeated the Darkness, but Dean wouldn't be looking at him the way he was, or feeling the way he was.

He still wanted the ground to swallow him up.

"I'm sorry," he began, like it even scratched the surface.