Sherlock jerked awake, skipping the continuously surprising realization that he had fallen asleep when he heard retching from the next room. He pulled back the covers and stumbled to the bathroom, where he found John on the floor, shaking and clutching the porcelain bowl. Tears streamed down his cheeks, and Sherlock could see him gritting his teeth and shaking his head even as he began to retch again.
Sherlock catalogued all these symptoms as he watched John huff out several muted sobs. John was sweating but not flushed, in fact despite the tears and the violent retching he was strangely pale. Sherlock narrowed his eyes as he watched his lover's left wrist twitch and noticed that even in his rushed hunch, John was favoring his leg.
A panic attack then.
Sherlock ran a frustrated hand through his curls. He would have preferred John were sick. Sick he could deal with; sick had symptoms and treatments. Sick was manageable. Panic attacks were not. And Sherlock loathed not being able to manage things. He waited impatiently while John's retching subsided somewhat.
"Would you prefer a bin? So you could sit more comfortably?" This was all he could offer. John nodded and stood shakily. Sherlock winced as John limped past and into the lounge where he curled up on the sofa. He retrieved a bin that he'd been storing under the sink since the first time John had leapt from their bed in a cold sweat. He walked out to the lounge and placed the bin on the sofa next to John, then retreated to his chair.
He would have preferred to sit and hold John as he shook, but he knew from experience that was the worst thing he could do. The first time, weeks ago when Sherlock had found John huddled in a corner and tried to comfort him, John had struck out and nearly broken his jaw. As much as it felt wrong to sit idly by and watch his lover suffer, Sherlock now kept his distance until John sought him out.
"Fuck!" John shouted. This was not unusual. John was normally more stoic, allowing frustration and anger to seep out of him in controlled amounts, but his control during an attack was threadbare at best. "I feel like my skin is crawling. Damn this stupid…" he broke off into another muffled sob.
There was nothing Sherlock could say, no words of comfort he could offer, no platitudes that would ease John's mind. There was nothing but this contemptible impotence that he could do nothing. If John had crosses to bear that were sometimes too heavy, than this uselessness was certainly Sherlock's cross.
And in this way they sat, John shaking and muffling his sobs, and Sherlock watching in frustrated limbo until the panic subsided and once again John was his own man. Sherlock could see when it faded, the blind panic that gripped him, but waited, fingers clenched into the fabric of his chair, until John held a hand out to him.
Sherlock was beside him instantly, the bin discarded to the floor and John in his arms.
"I'm sorry," John mumbled in Sherlock's chest.
"As am I, John. As am I."
In the morning, John would awkwardly try to offer an apology, and Sherlock would brusquely tell him not to be an idiot. Both men would smile a pained smile, both wishing they could stop the other from having to suffer through that again.