Sometimes it's a crowd. He hates crowds and yes, he's aware he lives in a densely populated city—the irony does not go unacknowledged.
Sometimes it's the television. The walls are thin and John watches too much daytime programming. They have several arguments about this.
It's not that he dislikes people (No, really!), but sometimes it's a person, and he can't stand listening to their inane chatter a second longer (mostly Anderson, especially Anderson).
Sometimes he has to push himself to solve a case and he doesn't have a chance to recharge in peace and quiet. At which point, he will completely shut down. He won't be able to speak; he can only curl into himself as his mind races in frantic circles. Sleep evades him despite his exhaustion. "No, no, don't talk to me right now," he'll say, assuming he can get the words to leave his mouth. This has offended several people, his shutdowns, but there isn't anything he can do about it. He's explained as patiently and as nicely as he can, the best thing they can do is to leave him alone—just leave him alone.
This has made finding a flatmate almost impossible, but John got over it fairly quickly, and John knows when those moods have descended upon his mind. Right now the curtains are drawn tight, and he's drawn his knees against his chest. He's wound up and tired and he doesn't have the energy to get up off the sofa at this point.
He's had to contend with the specter of Jim Moriarty. A painful ache spreads through his chest and seizes his mind. He hates to wait, but he's afraid of what will happen when it finally happens. He doesn't like this game—there will be collateral damage if he loses.
Sherlock hears the door downstairs open and shut, the familiar footfalls—John still has an irregular gait, he'd know it anywhere. John walks into the flat and sets a suitcase down. Loudly.
"So I'm back," John says, looks down at him. Several beats pass. This is the part where Sherlock is supposed to say something because that's how conversations work. John sighs and puts the kettle on instead.
A cup of tea is set in front of him and John goes upstairs to his room. Perhaps an hour passes until Sherlock leaves the sofa. By this time, the tea remains untouched and has gone cold. He drinks it anyway.
Sherlock creeps up the stairs as if he hasn't permission to go in there. He does; he doesn't know why, but he does. Why can he? He doesn't have to sneak, he doesn't have to knock, and he is invited here — at least for now.
"Hey," John says.
John is sitting in bed, looks up from his book. Sherlock sits on the edge of the bed and slides his body up so that his chest is pressed against John's hip, arches his back so he can see John's face. John has to put the book down as his personal space is slowly invaded.
"How was your trip?" Sherlock asks.
"Damp."
"Hmm."
"Get under here, then," John pulls at the covers underneath Sherlock. There's a rearrangement of arms and legs. He's invited here—to press their bodies together between John's thighs. Sherlock gives him a soft, lingering kiss. They're both too tired for lovemaking, but it's not what he had in mind. He'll kiss those thighs later.
"Would you do something for me if I promise to be nice to you tomorrow?"
"That depends on what it is. If it means getting up, then no." Quiet Exasperation thy name is John Watson. Sherlock presses another kiss on John's mouth and tries the wounded gazelle look.
"Pet me?"
The corners of John's mouth quirk up. "Where?" You're insinuating, John.
"My hair."
He shrugs in agreement and Sherlock rests his head against John's chest. He sighs as John lightly scratches his scalp and runs fingers through his hair. The tension slinks away for awhile.
"Thank you," he says, lets his eyes rest. As always, he's aware he should say something more, but his words tend to fail during these quiet interludes.
As soon go kindle fire with snow, as seek to quench the fire of love with words.
He'll read more poetry when he has time on his hands.