dean knowing cas for like 11+ linear years but also so much longer than that and so much deeper than that. like. if u count everything they've been through together. all the worlds they've travelled together, all the cosmic monsters they've triumphed together, the drinks and car rides they've shared together. thinking about the fact that dean fell in love with him along the way. how he must've thought about those feelings enough to question them, to question whether angels even felt human emotions like that. how he told himself they didn't. and then cas stood there infront of him, and told him 'i wondered what my true happiness could even look like. i never found an answer. becos the one thing i want. it's something i know i can't have.' and the way dean probably Felt That cos thats how he's felt for cas for so fucking long. then like everything that cas said after that? 'i know, i know how you see yourself dean. u see yourself the same way our enemies see you. you're destructive, you're angry, you're broken. you're daddys blunt instrument. you think that hate, that anger, that's what drives you, that's who you are. it's not. and everyone who knows you sees it. everything you have ever done, the good and the bad. you have done for love. you raised your little brother for love, you fought for this whole world, for love. that is who you are. you're the most caring man on earth. you are the most selfless, loving human being i will ever know. you know, ever since we met, ever since i pulled u out of hell, knowing you has changed me. becos u cared, i cared. i cared about you. i cared about sam, i cared about jack, but i cared about the whole world becos of u. u changed me dean.' and dean just feeling this for the timebomb that it was. knowing that no matter what he did or said, that his time w cas was almost up, so him saying the only thing that could make cas understand that dean Gets It, that he knows what cas is saying becos he feels the exact same way. him saying 'me too cas.'