Steve keeps one hand on his back, and the other strokes through Bucky's hair. Over and over, gentle and soothing (he hopes, oh how he hopes). Bucky's solid in his arms, and he hopes that he can be the same for him. A reassuring, grounding presence.

Bucky's breathing gradually smooths out, and the trembling stops.

Steve murmurs, "Good," and then to his great horror finds that he's brushed his lips across Bucky's.

No, you idiot.

Let the man calm down, without you trying to foist your own wants on him. Let him calm.