It's not that Sherlock hates his job. Sure, there's the extreme dislike for having to wake up at around 5:00 after staying up watching those ridiculous crime shows honestly how did they not know it was the brother it was blatantly obvious the second he had been introduced and don't even get him started on those forensics scenes dear LORD how do people even buy this stuff? (It's a guilty pleasure he doesn't understand he lets himself indulge in and one day he'll make himself stop, but for now there are dull television crimes to be solved with their daft detectives and overdramatic music playing and he'll be damned if they figure out who did what before he does.) His job is not so much terrible as well… it honestly is terrible. Not that it's a bad job, it's just dull. Tedious. Grinding coffee beans to be brewed into some blend or other, depending on what Greg has in store for the day. Watching Molly set out all the pastries she had come in an hour or so earlier to make fresh for the day. Checking to make sure everything is precisely where he left it once Greg had made him clean it up. Every day, the same thing over and over and over and over and it's 7:30. The morning work crowd is coming in. All here to get their caffeine fix and go because it's too hard to make their own drinks or whatever their issue is in the morning that simply will not allow them to brew their own bitter kickstart to their day.
Sherlock closes his eyes. Takes one deep breath in through his nose out through his mouth. Waits one more second. Opens his eyes and is now faced with having to go back out front because Greg simply can't take all these people on his own. Sure, Sherlock dislikes having to be confronted with all these idiotic people, most of whom who will be headed to an office building and working until 5:00 maybe 6:00 after most buy their simple large, black coffee and adding in whatever they need to make the simple brew bearable (they have a plethora of creamers, milks, sweeteners, and flavors located off to the side for those who can't wait for that to be added in for them, though Sherlock does notice how particular some can be about their coffees and teas and can respect that. He's been disturbingly picky about most things since a young age and not much has changed since then.) but he is not that heartless a man, though some will argue against that, and he knows that if he doesn't go out there there's a chance he may continue to find reasons to not come out in the morning and then he'd be out of the job, wouldn't he? So he walks through the door separating the eyes of the common public to the mysteries of the back room of a coffee shop (spoiler alert: it is not that mystical or magical) and Greg is telling him to take the next person and they settle into their rhythm of switching customers. It's quite terrible, just because Sherlock knows what they want to order as soon as he gets one good look, but Greg has told him not to tell any customers what they want because some people don't take kindly to being told those kinds of things. And why don't they? They're going to eventually tell him what they want, he might as well say what it is and get any awkward pleasantries and possible small talk out of the way as soon as possible.
And then he sees a new face. Sure, Sherlock gets those every once in a while, but that's normally in the afternoon not in the morning when the regular crowd comes in, those who know the menu and know what they wish to order, those who can get all of that mindless crap out of the way and then move over and let the next person through. But this new man is here and Sherlock takes all of him in immediately. He's short, much shorter than most men, but he holds himself high, back straight, looking up at the menu with their normal drinks and some special ones added in for the week or month or holidays (Sherlock will be the most grateful of them all once the scent of peppermint has been eliminated from the little shop he works in), blue eyes searching for anything of interest and then he's looking at Sherlock and saying something, but he's still taking this man in and learning all he can and misses the order. The man looks at him expectantly, waiting for some acknowledgment that his order was heard, that he'll be told how much it will cost, and then he can be on his way.
Sherlock blinks a bit and leaves his mind alone just in time to say "What was that?" before Greg has to come over and ask what exactly is going on, Sherlock, why isn't the line moving people are starting to complain.
"Just a large black coffee, please," the man replies, an amused expression on his face.
"Name?"
"John."
Sherlock nods, tells the man (John, his brain supplies) how much it will cost, adds the money to the register, hands him his change, and goes to pour the simple order into the to go cup he grabbed. He looks to where the man, James-Jacob-John is off standing and looking around the shop. And then his eyes land on Sherlock and Sherlock looks away and feels his face heat up slightly and isn't that a new feeling? Embarrassed? Nervous? He doesn't know how that man has had this effect on him, but he is going to find out because no one takes Sherlock Holmes off guard like that and no one has since he was maybe eight or so (childhood is so dull, who needs to remember all of those trite details, his science classes weren't even as extensive as he wished they were and had been deleted from his mind the moment he got his hands on a real textbook) and calls out the name he wrote down (again, John). He comes, takes the drink from Sherlock, nods his thanks with a smile, and leaves. No creamer, no milk, no sugar, no anything. Gone until the next morning, the next couple of days, weeks, months, years, maybe not even coming back at all. And Sherlock wants to know why, exactly, the thought of John not coming back bothers him.