Castiel doesn't let go, only holds Dean just a little bit tighter. He can do this now, hold him with all his might and not hurt him. There is something about that, the fact that they are on fairly even footing (Dean perhaps even 'outranking' him a bit so to speak) that feels comforting and right, as if they are now somehow where they were always meant to be. The physical sensation of having Dean in his arms is even more wonderful and he is in no hurry to let go of him.

"Yes. I'm sorry, Dean. It's my fault. I should have made more of an effort to contact you long before now. I feel like I haven't had a moment to even stop in a century, but there is nothing more important to me than you. If I had tried harder, you wouldn't have been subjected to this, I know that. I should have protected you." He was always failing Dean, he didn't even dare ask forgiveness anymore. He didn't deserve it and Dean would be crazy to offer it.