Depressing, Sam thinks.
Everything is depressing, from his aching body to the rain tracing its way down the window to the way Dean sings enthusiastically along to the mournful songs of love and loss that play endlessly on the radio. The not-Impala bumps over yet another pothole in the middle of nowhere gravel road, and Dean blurts a ceaseless stream of 'I'm sorrys' as Sam groans weakly and flinches, going white from the pain. He coughs, and a trickle of blood makes its way down his chin, white hot pain overtaking his body, and he vaguely registers the wheels bumping over the uneven land on the side of the road, Dean's voice muttering panicked reassurances. And suddenly it all becomes too much and Sam just can't anymore.
He hurts. So much, he hasn't felt good, or even just okay in such a long time and his body hurts—ceaselessly, relentlessly—constant, burning pain and Sam just can't.
It's raining and Sam is coughing up blood and its taste gags him, his eyes water as he coughs long and hard. His body hurts and he is coughing up blood and this is not the Impala. They are alone, once again, save for each other, and Sam is so tired. His nose itches and he can't stop coughing and blood, so much blood and his mind is swimming, and home is gone because this isn't the Impala and Dean is panicking and it's all wrong.
Sam feels the light as a feather touches ghosting across his shoulders, feels the hot breath of his brother's voice against his cheek as Dean props him against his own chest, supports him as he swipes a tissue across his chin and tells him to 'just breathe'.
The blinding, white hot pain consumes his body, and saps his strength as he sags limply against him. Tears of exertion stream from his red eyes, down his pale face and into his stubble as he gasps for air, clawing weakly at Dean's shirt.
And Dean's heart breaks just that much more as he cradles his weak (and not dying) brother to his chest, tissues scarlet with his little brother's blood scattered upon the stained upholstery of the truck that is so very, very not his Baby. He knows it, and feels that Sam feels this loss too, knows the sense of home it has brought the two of them since childhood (and in Sam's case—birth) has always done much to heal his brother's hurts. But he has done the best he can with what they have been given. And will continue to do what he deems best for his brother.
Dean is depressed. Everything is wrong, and Baby is gone, and Sammy is sick, and they can't finish the trials and though Sam tries to hide it, Dean knows he hasn't even felt okay in days, weeks… and Dean can't fix this hurt and this isn't something Dean can make better and it kills him. Nevertheless, he is considerate as he rubs along Sam's shoulders, not pulling him to his chest in a crushing embrace as he longs to, but lightly patting and stroking across the tops of his shoulders, offering comfort in the only way that does not hurt his brother. Not that he doesn't long to offer a firmer comfort, a comfort that at least makes him feel like he can help his little brother heal. And when Sam begins to claw at his shirt, completely spent with the force of his illness, Dean begins to feel his own walls crumble. The sheer fact that Sam has allowed himself this rare show of utter misery in front of him unnerves Dean, causes his own carefully constructed barrier to move. Because Sam is Dean's heart, and when Sam hurts, Dean hurts.
He begins to shush his brother quietly, running his hands through the tangled and sweaty mass of hair that hangs from his brother's head, pulling him close, disregarding the pain he might cause, and knowing Sam does too.
Sam doesn't care about the pain. Does not care. One bit. Because when Dean begins to card through his hair, shushing him and pulling him close—he can't help it. It's a feeling he hasn't felt in a long time, and he craves this: the one constant that has always brought him the absolution, the refuge, the love that he so craved. Dean. His brother, father, mother, best friend, confidant (at least for the better part of his life anyway, barring a few recent escapades). He brought praise, love, delivered scoldings, gave baths, kissed boo-boos—everything. Simply put, that was what he was to Sam: everything. And Sam knows—has always known- Dean reciprocates the sentiment, gathering him close, tucking his head under his chin as he breaks, releasing all the pent up and held in emotions that he has so carefully repressed in the face of being strong.
Sam has been through the mill, is absolutely run down, and Dean is removed to a time worlds away, when Sam was so small he actually used to fit beneath his chin, all of his legs in his lap, could be completely encircled by Dean's arms—protected. That's what he wishes his brother to feel, to be right now, what he loves having the illusion of doing for his brother as he tugs him to his chest, tucking his head under his chin, letting him push himself as close as he can to himself, shielding, protecting, letting him know he's loved. And in that moment Dean feels they have come perilously close to full circle, and the Sam he holds in his arms now is so near the version of his baby brother that returned to him ravaged and plagued by Lucifer's taunting and endless torture that Dean doesn't know if he can handle it. His brother releases soft groans and slight sobs against his collarbone, dampening the few inches of shirt surrounding the actual collar with tears of anger, frustration, hopelessness, sheer misery. And Dean understands. Because he feels that way himself, although the physical pain Sam is feeling surely can't come close to anything Dean has felt in his life, and how he wishes he could take it for his brother! But he can't. Because his little brother is honorable, noble, just, wants to take the pain on himself so that Dean doesn't have to but Sammy can't you see I have to!? Sammy it's my job to protect you! And Dean wishes, oh how he wishes, but at some point you accept the lot your family has been dealt, and just deal with your crap.
It is no surprise to Sam that, even through his own misery he feels so deeply the misery radiating off his older brother. And so he does what he does best. Blinking and sniffing mightily, he pulls himself out of the safe haven of Dean's chest, swipes a hand across his nose and says, "S'okay, Dean." But then a shudder runs through his frame, and the agony is back, burning fires into his bone marrow, the very fabric of his body, and he sobs again, back arching in agony. And when Dean's hand brushes his hair back from his face, tucking his face back into his shoulder, he relaxes.
Dean breathes out a chuckle at his baby brother, smoothing sweaty bangs from his face and shaking his head fondly as he pulls Sam's head back to his shoulder, feeling the shudder and gritting his teeth because he hates that this can't be fixed, and it's eating away at him to keep seeing his brother like this day after day.
Sam soaks in his brother's comfort, practically beaming through his tears, flourishing beneath his big brother's love, feeling the tenseness leave his muscles as Dean holds him close and rocks him, shushing him whenever he tries to talk, and alternating between smoothing back his hair and murmuring comforting platitudes into his ear.
Dean's own shuddering breaths begin to even out as he gets Sam to calm, and, slowly, holding Sammy in one arm and driving with the other Dean finds them a place to stay. And when Sam refuses to leave the shelter of his embrace for a shower, or even to change, Dean doesn't protest. He merely makes his brother as comfortable as he can, removing shoes and jackets, settling down on the bed with Sammy beside him, drowsily sinking into his side and nosing into his neck—still seeking the comfort that Dean was ready to give. And, for the moment they were alright: Dean 'big-brothering' and Sam 'little-brothering'. Although if Sam were conscious enough to voice his opinion Dean has no doubt he would term Dean's instincts more maternal than brotherly—and if he were to be completely honest with himself, Dean would have to agree. After all, a lifetime of caring for the kid has kinda stuck him in that position. And he doesn't mind. Not at all. Because Sammy, bitchy Sasquatch that he is, is Dean's heart. And Dean does whatever needs to be done for his heart.