Dean doesn’t smoke.
Not really, anyway. Once every year or so, he’ll get an urge and he’ll pick up a pack at the nearest Gas-Mart, and then he’ll stand around some motel parking lot and start one. For no real reason other than just to do it. The smoke will be harsh, but weirdly comforting as it curls against his lungs, and the cigarette will give him something to do with his hands. With his lips.
But no matter what else is going on around them—always and without fail—before Dean can even get two minutes in, he’ll catch a fleeting glimpse of Sam through the grimy window of their room. Or he’ll feel his brother’s eyes on the back of his head, anxious and sad. Dean will look up and he’ll meet his brother’s stare and Sam will always have the exact same expression pasted over his face. Every single time. A mixture between a carefully feigned lack of judgment, and a quiet, desperate longing for Dean to stop (as if lung cancer is something that either of them will actually live long enough to have to worry about).
It’ll be painfully obvious that Sam is deeply upset by the cigarette between his fingertips, but is also doing his goddamn best to stay out of Dean’s business and not bring it up. Because damn straight it isn’t any of his business. Dean is a grown-ass man and he can smoke if he wants to. Because they’re his fucking lungs. Hell, he can rip ‘em out and set 'em on fire in the freaking parking lot if he so chooses. His little brother has absolutely no say in what Dean chooses to do with his spare time.
And then Dean will sigh, flick the barely-used cigarette to the asphalt, grind it out with his boot heel, and toss the rest of the almost entirely full pack into the trash. Every. Single. Time.
And when he heads back into the room, Sam’s eyes will say, “You didn’t have to do that.” But his lips and his hands will say, “I’m so glad that you did.”