Work Text:
The first time it happens is in a clash of pain and thunder...
"Because I love you, okay? I'm in love with you!" The words are hurtled into the howl of the storm that's roaring around them. Dean's face is twisted in grief and rage. His mouth works as if speaking those words has caused something inside him to bleed. They almost lost each other again -- more stupid self-sacrificing bullshit on both sides -- and Dean is angry, and he's tired. He's exhausted to the core, so utterly over this cliched repeating trope in their lives. He wants to get past this and get to the part where they can have a life, maybe even a life together. So it's not like he means to say it, but he's beyond ready to say it when it finally comes out.
And after that, everything changes. Things get so damn good. The two of them together, in the Bunker, in their bed, in a relationship that's so much more than either of them ever hoped. Dean's unbelievably fucking grateful, and he never wants to forget all that it took to get them here.
So when they have their First Fight™, about something stupid and domestic like which way the toilet paper hangs or whose turn it is to clean the hair out of the shower drain, Dean flashes back to that moment in the rain. The heat this petty squabble was generating inside him disappears in a heartbeat. Who cares about this penny-ante bullshit when they both almost died a million times trying to get to each other for good?
Cas is still riled up about the chore chart or whatever, thoughts on a different page entirely from where Dean's mind has gone. So when he growls, "Why?" he's not expecting the reply he gets.
"Because I love you, okay? I'm in love with you." Dean says it softly, with a crooked smile, all so different from before.
Cas gets it immediately. Their argument dissipates into the ether, dispersed by a healthy dose of perspective. What's a dirty countertop compared to everything they've been through?
After that, whenever words get heated between them, the little bickers and irritations of marital life, one of them will say it: "Because I love you, okay? I'm in love with you." It never fails to bring them back to center and remind them of how fortunate they are.