Some Kind of Pain by bactaqueen.
A bittersweet and heart-wrenching thing. A real gem, a hidden treasure of the Marvel fandom IMHO.
Steve trembles like he's trying to hold himself together, like he's struggling for control. Sam shoves his hands under Steve's shirt and digs his fingers into the small of Steve's back. I've got you, he wants to say. I've got you and we're not going anywhere.