A/N: This accompanying song is called "Leave Right Now" by Will Young.

Disclaimer: If you recognize it, I don't own it.

~I wouldn't know how to say
How good it feels seeing you today
I see you got your smile back
Like you say, you're right on track~

Castiel was still brooding in the corner and Dean just about had enough of it. "Jesus, Cas, come on! You can stop your sulking now, we're all good, we're all in one piece."
The angel looked up at Dean and raised his brow before shrugging a little sheepishly.
"I'm sorry Dean, it's just.. I never should have endangered you in the first place. I shouldn't even still be here right now."

Dean sighed and stood up from his place at the table where he had been happily stuffing his face with any food he could find. He made his way over to Castiel and sat on the bed in front of him. "Cas.. Cas! Look at me." Castiel turned his eyes upwards and looked into Dean's. Beautiful and bright and green, just like nothing ever happened.
"Cas, I'm fine, okay? Could you at least stop being such a downer and just.. Hang?" Dean asked, slightly frustrated at his off-putting demeanor.

~I'm here, just like I said
Though it's breaking every rule I've ever made
My racing heart is just the same
Why make it strong to break it once again~

Castiel took a deep sigh. He wanted to scream out that he had to leave. That he couldn't handle looking at Dean and remembering his lifeless body. Because of him. And him selfishly staying here, simply because he couldn't bear to say no to Dean, was only putting him and Sam in danger, again.

But no, he had to go and get himself roped into staying here again. Dean's silent pleas and Sam's puppy dog eyes convinced him that "Just one more day, Cas.." would be fine. Even though he knew, he knew, it wasn't going to be fine. It would never again be fine. Simply because Castiel couldn't stand to think that he had almost lost the one person he felt deserved the happiest life the most. That that man, who knew all his secret hiding places, somehow had refused to give them up while being tortured to near death, because of him. Because of some fake sense of obligation due to the fact that he was the angel commanded to pull him from hell. Dean didn't owe him anything. Castiel, on the other hand, felt he owed Dean everything.

~I'm a little more careful
Perhaps it shows
But if I lose the highs
At least I'm spared the lows~

Even Sam had noticed Castiel's detached behavior the last couple of days. It was like he was there, yet he wasn't. Not really. When they were talking to him, he barely even reacted. Dean even tried to make some movie references, just to see that trademark eyebrow lift followed by "I don't think I know that reference", but nothing.

And of course, Sam wasn't an idiot, like Dean and Cas. No, Sam was the outsider looking in on the situation. Sam saw perfectly clear that Cas held adoration for his brother way beyond the 'best friend' boundries. And Dean was.. Well.. Dean was Dean. He tried to make a joke of everything, he tried to pretend that nothing happened, put his walls back up to way over yonder, all the while trying almost desperately to get Castiel's attention. And the way those two were just practically drilling a hole in the each other's heads with their eyes while the other person wasn't looking was becoming downright ridiculous.
But of course, Sam had to keep his mouth shut. He'd tried talking to Cas, first, but Cas just kept throwing it on the "This wasn't supposed to be your fight" pile. And of course, when he went to confront Dean, the walls shot back up and he got a "What the fuck is wrong with you, man?!" response that seemed to be code for "Drop it now or I won't hesitate killing you in your sleep."

And then there they were, barely a week later and Castiel was announcing his departure back to Heaven. And they were shocked, yet not really. And Dean was angry, nay.. He was furious. He was throwing a major guilt trip on Cas, unfairly so, about how it was his fault in the first place and how he owed it to them to stay to make sure they were safe. And when Cas finally couldn't take the verbal abuse any longer and literally walked (not wooshed) out of the door, Sam couldn't bear to stay out of it any longer.

"Cas... Cas wait!" He called after him, after they both turned the corner at the end of the block. Castiel came to a standstill, his back to Sam and moved his hand to rub his forehead with a loud sigh. "What, Sam?" He simply asked.
Sam moved to stand in front of him and looked at him with pleading eyes. "Come on Cas.. What's really going on here? Tell me the truth."
"I can't do this anymore, Sam.. I can't just sit idly by while you and Dean get hurt because of a war you have nothing to do with.." He sighed again, but Sam looked unimpressed. "Stop lying to me, Cas.." Sam tried again. Castiel turned back around, away from Sam and wooshed away, back to the motel room, presumably to say goodbye. And if Sam hadn't been paying attention, he probably would have missed the words that came out of Cas's mouth before he left. "He deserves so much better.."

~I think I'd better leave right now
Before I fall any deeper
I think I'd better leave right now
Feeling weaker and weaker~

There were so many reasons for Cas to leave. But only two were important enough to actually go through with it. To actually make himself cut ties with the Winchester brothers. The first was that he simply couldn't handle feeling what he felt for Dean without sooner or later 'slipping up' and making a mistake he couldn't come back from, ruining their friendship forever. Better to break your own heart, before it gets broken by someone else, right?
The second, more prominent reason, was that Castiel had to settle this war, and it had to be settled now. If there was one thing he was never going to let happen again, it would be Dean getting hurt because of something he caused. Something he could prevent from happening.

So Cas did what had to be done. He cut ties. And he cut them good. Maybe not with Sam, Sam would likely understand his point of view, but Dean, Dean was a whole other story.
"You had better not be fucking leaving us again, Cas.. Castiel!" Dean practically yelled at him. He didn't understand. And he was angry, at so many things. He was angry that his friendship meant so little to Castiel. He was angry that he hadn't come when he called for him all these past months. He was angry at himself for feeling things he shouldn't be feeling for his best friend. And most of all, he was angry for Castiel carelessly breaking his heart by leaving again. The torture he could take, hell, he would pick being tortured every single day if it meant Cas not leaving him.
And just before Castiel made his way back to the sky, fighting a fight that simply had to stop, he stopped and turned to look at Dean. One last look into those beautiful green eyes. "I can't keep on saving you, Dean." And with that, he was gone.

~But you may never know why
Once bitten, twice as shy
If I'm proud, perhaps I should explain
I couldn't bear to lose you again"