I just think that’s amazing. Castiel was lost. He didn’t know whether or not he was good or bad after what he had done, and he didn’t know where to go. But then he took a piece of Sam into himself. It may have only been the painful, broken part, but it was definitely a part of Sam, because Sam hopes, Sam never gives up or gives in, Sam only sees the good he can create in the world, even with all the other burdens he must carry. Even when Sam was dying of pain he took the time to share a candy bar and help someone else in need. So Castiel took all that pain from Sam, but with it I think he received a little bit of that wonderful humanity that is a part of Sam Winchester. It’s as if when that happened, Castiel understood a little more about what it meant to be human, and that it saved him from tearing himself apart by guilt. I think he understood that even through the pain and the doubt, with everything falling apart, you should never lose hope and never stop fighting for what little good is left. He learned that, I think, from Sam’s pain. Sometimes I feel as though Sam’s character is so under appreciated and needs so much more exploration because he is a truly amazing person. He made bad choices, just like Castiel, but he never let it stop him or even slow him down, and he is always able to show compassion and understanding for those around him, even though he’s been through hell and has so much more to complain about. That’s the person that saved the world, and the one that saved an angel.