Falling is just like flying.
Losing his grace was the most unexpected way Castiel thought heaven would use as a punishment.
Being with the Winchester's has it's perks, and being with Dean was honestly the only thing that keeps him alive. It doesn't matter how unrealistic it may seem. And somehow he understands that their relationship ,helps Dean too, if only a bit.
The hunter had and will always be there for him. Always willing to help no matter the cost or for what. His electric green eyes blazed slightly when Castiel would tell him about what heaven did to him or earth and whenever he talked about what heaven was planning on doing, or sometimes they filled with concern and a hint of sadness and he stayed close to him.
He remembered an old expression, that stated how actions spoke louder than words and whenever Dean would hug him or kiss him softly, promising to be with him, the expression would suddenly make sense in his mind.
And sometimes when Dean would gesture with his hands to sit with him or lie with him and they would talk and talk, until The morning darkened, the expression got a little dimmer. But that's not important.
When Heaven decided that they would no longer turn a blind eye to the fact that Castiel, in no way, will ever hurt the Winchesters, they found no use for him.
It didn't even pass the angel's mind.
The tips of his wings beginning to turn into a soft grey, slowly but surely, barely noticeable. Once they were seen Castiel put it down to the aftermath of a simple fast flight, although he did get a little twinge somewhere.
After all, feathers were known to be delicate things, even if in reality they were the only thing most angels depended on.
Then the grey got darker and duller until it merged into a horrid black and blossomed outwards, contaminating the others.
And that was when he finally understood. When he realised what was happening.
In hindsight, if he had dwelled on that twinge a little longer, he could have realised earlier.
And, perhaps, they could have stopped it.
Him and the Winchesters.