It was the little things that Castiel always found himself struggling to understand. Sunsets were one of these things. Well not sunsets themselves, that was the easy part, that was the earth spinning. No, it was what people saw in them that puzzled him. Days and nights were still a sort of novelty for Cas. He didn't need to sleep and in heaven days and nights were relative and his time on earth had been tumultuous enough that any sort of circadian rhythm was out of the question.
So as Castiel sat on the bus holding the tablet, he began to realise that hunting and travelling had meant that Dean and Sam must have seen thousands of different sunsets. Long orange evenings on warm days in summer. Coloured clouds burning with orange or purple and moody or pink like candy floss. And then the way in winter the sun slipped out quickly, dumping the world into darkness. A little different each time and never quite the same. So for Sam and Dean the sun was a constant, no matter how dark the days go, no matter how long the night, it always came back. In a chaotic world it seemed like this was a reminder that the earth was still spinning, this must give them hope.
That morning he had actually watched the sunrise properly for the first time and for the first time Cas got an inkling of what it was like for Dean when he didn't come back when he called. When he didn't appear. For a moment he realised how soaringly unpredictable he must seem.
Unlike Dean. Dean was loyal, Dean was like the sun, he always came back, always held on.
And Cas knew he couldn't always meet Deans expectations but they were often unreasonable. He was an angel and sometimes more power meant… the phrase "more responsibility" popped into his head. Dean again on one of his movie marathons he made Cas sit through. He wondered if that was what it was like to think in movie quotes all the time.
Castiel wondered about a lot of things. Like how grounded being with the Winchesters made him feel.
So this evening he went back to watching the sun set and thinking about Dean, because that is what relaxed him, that is what made him feel better. And the moment flashed into his mind again where Dean had made him come back to himself.
Castiel usually tried not to feel too much. Cas had too many things to feel bad about, he had had to say sorry too many times. To too many Deans.
And tonight the sun set again, like it always did. And it would keep doing until literally the end of days.
Tonight Castiel remembered that Dean was temporary, a blip in the lifespan of the universe, despite being stubborn, determind and powerful enough to avert the apocolypse and defy death.
That this sun would not be around forever and this fact had never bothered Cas more than now.
Right now though, the thought that was running underneath all this was simple; Castiel you will fall and you will be stuck here, trapped on this spinning world and you will wait for the sun to come up and go down to mark out your days for as long as you live. There will be no more skipping in and out of time, in and out of dimensions.
And it wasn't that he could never go home.
It wasn't that he would never see the angels again.
He had cut that connection long ago. Castiel had expected to fall, to die many times before and he hadn't known he would come back.
It wasn't that he was scared of losing himself. Dean knew where he kept that. Dean knew better than he knew himself.
It was that this home was fleeting.
If he stayed, it would hurt so much more when it was gone.