Every day after their fight, Dean prayed to Cas to come back. It had been another stupid fight about everything and nothing, but this time Castiel had been gone for a week and still wasn't answering when Dean called. Dean was getting more and more desperate to fix things with his angel, every time Sam wasn't in the room Dean would stop everything and just pray to Cas, begging him to come back, mentally screaming that he was sorry.
Sam could tell that something was wrong with Dean, and it obviously had everything to do with Castiel, because obviously, to everyone except the older Winchester and his angel, they were in love. He thought that Dean and Cas may have realised when he started dating Gabriel, but apparently this was not the case. Instead they continued with their longing eye-fucks, until Dean got too drunk and Sam could see his true feelings rising to the surface, only to be buried by harsh words and alcohol.
Finally, Sam and Gabriel had had enough of both their brothers; they decided it was time for a divine/human intervention. Sam sat down to talk to Dean and Gabriel fluttered off to talk to Castiel, both coming back to conclude that their brothers were miserable idiots.
Eleven days after their fight, Castiel appeared in front of Dean, who was contemplating a bottle of whisky. The Winchester glanced up but didn't really have the energy for much else, he hadn't been sleeping well, and food had lost its appeal.
"Hello Dean." The angel said, voice ready to break at any moment.
"What, now you only come when I don't call?" Dean's voice was hoarse from lack of use.
Cas stared at him for a moment before suggesting "If you don't want me here, then perhaps I should leave?"
Dean knew Cas was about to take off again, and who knew for how long this time, so he grabbed the angel's wrist and almost yelled "No! Stay, please..."
He looked up at Castiel's face, seeing the tension drop ever so slightly from his features and Dean started fresh "Look, Cas, I'm always a complete jerk to you, and I don't mean to be, it's never what I want to say, it just comes out. Sam and I had a talk-"
"Gabriel spoke with me also." Cas interjected.
"-yeah, truth is, Cas, I've been completely miserable since you left, and Sammy and Gabe are happy, and I-I want that with...I want that with you, Cas. I'm just scared of fucking things up and losing you, but Sam made me realise that I'm already doing that. I just need to know if you can forgive me."
Castiel tilted his head, trying to comprehend what Dean was actually getting at, this frustrated the hunter, so he did the only thing he could to make the angel understand.
He kissed Castiel, crushing their lips together, after a few moments Cas relaxed against him and Dean put an arm around his angel's waist.
When Dean pulled back from the kiss, Cas looked a little intoxicated as he smiled blissfully, and Dean couldn't help but smile back "Get it now? I love you, you stupid, adorable angel."