It had taken years, it had taken more than Hydra, more than Thanos, more than anything combined, but finally the cracks in the chassis that kept Bucky together day in day out were giving, growing like spider's webs. They were like a dam holding back not a wall of water, but a wall of emotion which Bucky had suppressed for too long. Sure he'd had moments of anguish when he'd first fallen, when Hydra had turned the screws to him, when he'd thought he'd never seen Steve again.
But just like that, feeling Steve start to sob against him, feeling the telltale signs of a Steve Rogers panic attack (which he couldn't even remember Steve suffering since he became a super soldier, and that was a whole set of memories that was making Bucky crumble all the more faster) had Bucky crumbling once again. But it wasn't due to Thanos, it wasn't anything dangerous or anything, Bucky was still a hundred percent flesh and blood (and Vibranium steel) all wound together and still standing despite it all. But he was crumbling, those years of pent up emotion, of loss, of despair, of mind-numbing survivor's guilt and PTSD that kept him from sleep and at times from eating... all those years had finally come to a head.
But it didn't matter because Steve was here. They were crumbling, they were falling once again into that abyss, but they were together, once again, as it was supposed to be. Bucky felt himself shaking violently, all traces of resolve quickly dissolving as he felt Steve against him.
"Hey... hey, hey, hey, Rogers," Bucky said firmly, his own voice shaking with barely suppressed emotion, "That's not on you. It's not on anyone but Th-- him. He got the jump on all of us. It... it could have been anyone of us. It could have been you." He didn't understand the whole Gauntlet thing, how Thanos could snap his fingers and erase 50% of living creatures just like that, but it must have been random, it could have easily been Steve.
Bucky pulled back just as Steve did, keeping him close and as he looked at him he felt the tears finally start to fall down his cheeks, his lip trembling, his fists clenching into Steve's shirt, one of his hands moving up to brush through Steve's hair. He had to focus on breathing. In, out, in, out. He felt like he was on a rollercoaster that had taken him six loop-de-loops in a row and his mind was still racing to catch up.
"Hey." Bucky managed, shakily giving Steve a smile, before he started crying too, pressing his forehead against Steve's. "Look at us macho super soldiers all going to pieces. Ah shit. Too soon." He huffed out a laugh, gripping Steve's shirt tighter, his other arm wrapped around him, still keeping him as close as possible.