((So this is my first Destiel fic, so please don't hate on me if I messed it up somehow. Please give me constructive criticism!))
"I'm sorry, Dean," Castiel said seriously. He still had an old rag pressed to the gash in his cheek.
"Seriously Cas, it's fine. We took down the ghost, so it doesn't matter," Dean responded, his eyes flickering to the bloody rag, barely able to restrain himself from taking his eyes off the road altogether. After all, his- no, the fallen angel had been stabbed in the cheek with a rusty nail that the ghost had flung at him.
Cas been preoccupied with digging the nail out and finding something to compress it, the human pain had been too much for him to bear so he couldn't help exorcise the ghost. The fallen angel blamed himself for not getting over the pain sooner, although Dean blamed the ghost for hitting him, and himself for letting Cas come with him so soon after his falling.
"I'm useless now, I really shouldn't be accompanying you on your hunts. I'm not needed, I'm just getting in the way..." the injured man said.
"Nonsense! How many times have you seen me or Sam get hurt on a hunt? It doesn't mean you're a bad hunter."
Cas looked doubtful, but he stopped talking.
As soon as they got back to the Batcave, Dean flopped back on the couch to take a nap. Castiel paused, his eyes raking over the tired form of the elder Winchester before heading to the kitchen to see if he could help the younger with anything. Dean slipped easily into sleep, beginning a new dream.
Mary Winchester stood next to Dean's children's bed. She smiled softly at her drowsy little boy who was gripping her dress tightly in his small fists. Her blonde hair fluttered slightly, as if there was a light breeze, and she glowed like she had laid in the summer sun for hours and absorbed it all.
"I don't want to go to sleep now, I want to stay up with you," Dean insisted.
"You'll be tired in the morning if you don't. I'm going to bed now too."
The child scowled and declared, "I'm not tired."
"How about I sing you a lullaby? It's been so long since I've sang you one..." Mary said, thinking briefly about her other boy, the one sleeping in the crib in the other room.
Dean nodded, trying to remember how long it had been since he'd been sung to by his mother. Her voice was so pretty, and he loved to be doted on. She kneeled by his bed and smoothed his hair down before she began singing. As the first words came out of her mouth, the scene changed and Dean and Mary disappeared.
"You are my sunshine, my only sunshine."
Visions of Castiel were all that were visible. His glowing aura and dark wings spanned several yards. Cas had his rare smile on his face, eyes all alight and happy. His smile is that of a human, like the ones he smiles now that he's fallen, even though he's clearly an angel in the visions.
"You make me happy, when skys are gray."
New visions replace the last. Now it's all the times Castiel has made Dean laugh, or when he's misunderstood something and has done the classic Cas head-quirk. More images are brought up, these are all of Dean's imagination. They show Dean pushing the smaller man against the wall and kissing him, or holding him close at night, or going out to eat together and not talking about hunting or angels.
"You'll never know, dear, how much I love you."
Dean suddenly pulls away from all of the visions, now he's a hundred yards away from them. He sees how Cas is so oblivious to human emotion, how he would disappear as an angel, or how he'd turn his back on him and not care that Dean's heart just broke a little more. The tortured Winchester trys to move, to go after his angel -fallen or not-, but he can't. He's stuck.
"Please don't take my sunshine away."
He can't move as he watches Cas's return to him, after the fall. He watches as that just-turned human Cas changed into the Castiel from 2014. The drugged, hurt, cynical, hopeless, human Castiel stared at him as he cocked a pistol. The fallen angel put the barrel to his temple and waved a little before pulling the trigger. A burst of red splattered from the other side of his head right before the man slumped forward, dead.
"No!" Dean yelled as he woke quickly, sitting up in a rush. Castiel stopped as he walked in the room with a pile of books that Sam had wanted put back on the shelf. The freckled man stood and crossed the room quickly, grabbing Cas by his biceps and shaking him slightly. The books clatted to the floor as the fallen angel stared, completely perplexed, up at him.
"You aren't useless. You're the baddest motherfucker I know, even without the angelic mojo. And even if you aren't needed, you're wanted. Dammit, Cas, haven't I told you that you've got family here? I love you, okay, so you can't leave," Dean blurted before he could stop himself.
Then, like he'd imagined at least a million times, he pulled Castiel forward into a kiss. After a brief pause, Castiel responded in turn. The kiss was long, passionate, and perfect in Dean's opinion. When it broke, Dean stared at him for a moment before asking, "Damn, where'd you learn that?"
A small blush appeared on Cas's cheeks as he muttered, "The pizza man."
The older Winchester burst into laughter, "You're too cute!"
Cas scowled, embarrassed and upset, "Aren't you going to listen to my reply, Dean?"
He quieted and nodded, so Cas responded, "I love you, too."
"It's about damn time," Sam commented from the doorway.