There are good days and there are bad days.
Today is a decidedly bad day. In fact, it starts out merely bad (he jolts awake at 7 o'clock in the morning after a particularly restless night, his arm aching and his neck annoyingly stiff), graduates to Bad around midday (all of the experiments in the kitchen are wrong and boring and he wants to just bin every single one but he can't because he knows that tomorrow he will want them, probably, when this passes), and ventures into Very Bad territory about an hour after that (not even the violin is helping because every single piece he plays isn't right, it's too loud or too soft or too adagio or allegro or vivace, it's just wrong, all wrong, all rubbish).
It is around this time that Sherlock realises he's relieved John isn't here. That he's at the surgery, working, curing people, fixing up a fraction of a fraction of all the world's wrongs, making a negligible difference. Oh, there's a part of him that wishes John were in the flat, but it's a small part, an irrational part, and irrational parts are irrelevant to the whole.
No, it's better that he's alone. John would just get in the way. Might even make It worse. Probably hover about, asking questions, treating him like a patient. (He hates being a patient. It's nearly as bad as being a doctor.) Too much to deal with.
Better to be alone.
By half past one, he has made a mess of the living room. Books lie abandoned, face-down on chairs; at least four experiments have migrated from the kitchen; sheaves of paper carpet the floor. He manages to get an absurdly long paper cut on the sole of his foot, and swears so explosively he half-expects Mrs. Hudson to come bustling up and see what the shouting is all about.
He very nearly wishes she would.
He needs to be moving, needs to be doing something or he'll drive himself insane before he gets another case, and that won't be good. Not good at all. So he cleans the flat.
It takes him four hours. He makes himself do it, even though it borders on being physically painful. (It isn't actually, except for the moments when he nearly convinces himself to give up. Then he deliberately presses the sole of his right foot into the floor and lets the stinging pain dissuade him.)
(And it should only have taken him two and a half hours, but he'd gotten—distracted, stuck, tunnel-blinded while he reorganised the bookcase. And it had been another mark of his failure that he'd only snapped out of it after his mobile went off. Unlisted number, a caller who hung up as soon as he'd answered with, "Sherlock Holmes." Mycroft.)
The accompanying feeling of accomplishment is faint and fleeting and an utterly crap reward for the amount of time spent.
He cradles it to himself for as long as he can.
John comes home late, bearing gifts of curry and chicken masala and basmati rice and three different kinds of naan, and it very nearly makes up for the searing, sickening irritation that squeezes Sherlock's lungs the moment his flatmate starts nattering about the surgery and the patients and Sarah, being stupidly obvious in his attempts to draw Sherlock out of his head and into conversation.
(And it reminds him of why he hates people, why it's better to deal with this alone. John may know, he may accept Sherlock as he is, but he can't understand, not when his brain is wired just like everyone else's.)
He eats his dinner mechanically, silently, just to be doing something.
The box is old and wooden and plain, with a broken lock and hinges that probably need oiling, and it lives inside the nightstand beside the bed he rarely uses.
He hates sleep, hates it for being a total waste of precious thinking/doing/observing/deducing/experimenting time, but right now, at this moment, all he wants is for this to go faster, for this wretched day to be over. Except he knows his body, and he knows that tonight, it will resist sleep no matter how much he wants it, and that is what the box in his lap is for. His legal box. The one with the cigarettes he refuses to smoke, the nicotine patches he needs to buy more of, the sleeping pills that he rarely takes. His safe box.
(It has a twin. This is the ugly twin; the other is beautiful and dangerous and it lives in a dark place that only Sherlock knows but will never go back to. Never. This is his life now, not that. It will never be that again, and, oh, how he misses it sometimes.)
He caresses the cigarettes, counts the patches, downs two of the pills, and waits for sleep to make his eyelids heavy.