Disclaimer/Spoiler: I do not own Supernatural or anything else involving the great TV series. This story is based off of the ending of Season 7 premiere, Meet The New Boss. I just made it my own from my imagination. Enjoy!

I Failed You This Time

"Cass, you child. Why didn't you listen to me?" Dean muttered in distress, kneeling down by Castiel's side.

"You, you got me thinking it'll be alright
You, you told me, "Come and take a look inside"
You believed me, every single lie
But I, I failed you this time..."

Cass was doing things no one would ever approve of. First, he started a Civil War in Heaven to prevent Raphael from starting the Apocalypse all over again. With no other choice, Castiel had joined forces with Crowley, the King of Hell, to claim the souls of Purgatory. Of course, he was only trying to accomplish a good deed, but he only caused mass chaos. He ended up betraying Crowley and obtained all souls of Purgatory, ensuing in his powers to reach the level of a god but at a deadly cost: the power that the evil souls have granted him has distorted Castiel's mind, causing him to declare himself as the new God.

However, since Cass or "Godstiel" was extremely powerful and on a raging killing spree, Dean orders Death himself to kill Castiel. It was obvious that he didn't actually want him dead, but Cass needed to be stopped before something worse broke loose (like the Leviathan, one of the seven Princes of Hell and it's gateskeeper, unleashes and is actually holding on inside of the angel). Dean and Bobby Singer wanted to help Cass, but as he lied motionless and cold on the ground, it seemed as if nothing was possible for him to come back.

"I was waiting for the day you'd come around
I was chasing, but nothing was all I found
From the moment you came into my life
You showed me what's right"

Not two seconds later, the angel was greeted back to reality; all the blood and scars from his face had rapidly vanished like water to vapor as Castiel gasped profoundly for air. He may have been an angel, ones who show no emotions or feelings, but his mellow, terrified bluish-gray eyes told a different story.
It took Dean a few seconds to realize what was going on when he first saw Castiel struggling on the hard ground. His mossy green eyes lit up like streetlights on a dark highway. He's alive.

"Cass?" he said in bewilderment, as him and Bobby assisted his beaten vessel up off the ground gently. Cass was still frail and shook up by what all went on, feeling like the world was moving underneath him. "Hey, hey- I got you."

Castiel's limp, fragile body fell in Dean's arms, pulling him closer to his chest for a supporting hug. Dean was so relieved to see his friend awake once again. Losing him would have be one of his worst nightmares…
Cass shifted his weight and pulled himself together and out of Dean's grasp.

"Well," Castiel stated in a blank and groggy voice, "that was unpleasant. How... am I alive?"

"It wasn't easy," Bobby began calmly. "We were just trying to save the world."

"Just be glad that you're back with us," Dean replied in more of a stern voice than caring. Now that he had Cass back, it still didn't change how annoyed he was with him for lying and pushing him and others away. He wasn't going to forget that.

"I never felt like this before
Just when I leave, I'm back for more
Nothing else here seems to matter"

"I am ashamed. I failed you. I'm sorry," Castiel frowned, staring at the ground for a brief second melancholy before returning his eyes back at the two men. "Thank you, both of you. I'm going to find some way to redeem myself to you."

Dean shook his head. Cass had to do a lot more than apologize to gain Dean's trust back. Everything Cass had done appalled him so miserably, so it wouldn't be to anyone's surprise that Dean would never forgive him, but Cass was that stubborn that he knew he was going to make it up to him, one way or another. You aren't going to win me over with that line.

"Well, we'll see. Come on," Dean replied coldly, turning quickly on his heels.

"I mean it, Dean." Castiel proclaimed in a firm tone as he reached out for Dean's hand, gazing back at him with pity. Even though he was an angel, Dean was expecting him back-off and keep walking, but no. Cass was dead-on set at making sure Dean would trust him again. He was a bit speechless at first, but nodded.

"In these ever changing days
You're the one thing that remains
I could stay like this forever"

"Oh-kay, well let's just find Sam, alright?" Dean answered back wistfully, gripping Cass's hand tighter.
But it was only a matter of time before evil played its role again, and Castiel would no longer be there to gain respect.

"And it feels like tonight, tonight
And it feels like tonight
'Cause there's nothing that I wanna do
But try to make it up to you
And it feels like tonight, tonight"