1

His hand was wandering over the soft skin of John's abdomen, the other man pulled close to his chest, fast asleep and completely limp in his arms. Sherlock's mind, on the other hand, was anything but relaxed. Last night it had all seemed like a very good idea. John had been so close and he had wanted, wanted, and in the end they had both given in to what they had denied themselves for ages and it had been glorious. Even an hour ago, when Sherlock had woken up, he was still over the moon with that decision, John's back so warm and cosy against him, Sherlock's whole consciousness hazy as he could nuzzle the short hairs in the other's neck. Though after a while of lying still, his mind had kicked in and now he was panicking. There had been reasons why they hadn't been doing this already. Good reasons. A friendship that he didn't want to ruin, not ever, because it was better than anything he could ever have hoped in that direction. They worked together. Sleeping together would make everything complicated. But he was Sherlock Holmes, obviously he could manage complicated, it wasn't just that.
Love didn't exist. It was only a man-made concept, like time, but time was a manner of measuring something that did exist, that was visible as the sun made its way around the earth, that was visible in all its consequences. Love, on the other hand, was just a name for a bunch of feelings, and feelings were just games of the mind to create difficult situations. Without the distraction of emotions, it was so easy to be efficient, to keep working, to reach any goal. Feelings were like a thick fog in one's mind, only sharpening to the one object the emotion concerned.
What love really was, was a reflection of the need for proximity to another human body projecting on the nearest person, probably initiated by one of the evolutionary developments, combined with the fact that having someone around was an extra protection, an extra couple of eyes warning for predators.
Only, being alone was what reallyprotected one. Emotions for another person made one vulnerable. Decisions would be made in order to achieve the best for the person they "loved", ignoring what was the most intelligent to do on all areas.

This, this was dangerous and not in the way to which they were addicted.
A mix of sense memory and imagination, nothing more. Nothing real.

He sighed and pressed his face into John's shoulder, the familiar scent welcoming him. John let out a soft moan in his sleep, and as a reaction Sherlock's thoughts decided to terrify him. I love him, they said. His eyes snapped open, filled with pure fright that no-one would see in the darkness of the bedroom, and he untangled himself, careful not to wake John. It was better if he wasn't here when the other woke up, otherwise there would be no way back.

2

John woke up very slowly. The bed was warm and something good had happened last night and the pillow smelled a bit of Sherlock and that was very nice. For a while, he didn't register or recall anything but those notions. Then he realized that something was missing and he opened his eyes, wearily.

He found Sherlock completely curled up in his chair. His dressing gown had fallen off his right shoulder, but clearly he hadn't noticed that, neither the fact that he was freezing in the living room with only the gown not even covering all of his body. His head was pressed between his knees, his arms too tight around his legs, and John sighed.
"Sherlock."
He didn't get a reaction, but honestly he hadn't expected one. It was all too clear what was going on in Sherlock's head. Perhaps it was surprising that this mood hadn't shown up the night before. He kneeled before the tall man's chair and gently touched the wrist of Sherlock's right hand, the one that was clinging onto his other wrist to make sure that he was folded into the smallest ball he could. Sherlock didn't pull back. It was a small triumph.
"Sherlock, can you look at me?"
Apparently not.
Another tactic, then. John started talking in a soft voice.
"It's fine, Sherlock. I enjoyed it and if it-" He shouldn't say frighten- "if it is distracting you too much we can keep it there, we don't even have to talk about it, but please don't feel guilty. It was far too amazing to feel guilty about, right? It's fine if you just want us to be friends, it's all fine."
"Except that it's not." Sherlock's voice was muffled by his knees and he sounded far more unsteady than John had ever heard him, and then he was counting the time when he was drugged by the mists of Baskerville.
"Why not?" John asked.
"I can't just leave it... like this. I am too... invested. I'll want it again." Sherlock still didn't look up.
John moved his hand to Sherlock's shoulder and let his fingertips graze over the pale skin. "We could come to an agreement."
The sound was almost inaudible, but still John recognized it as a sniffle. He stood up and cradled the man in his arms. "Or we can take this much, much further," he whispered. "We can just admit that we love each other and live together, even more together than we did, and never feel guilty about it because we would make it work."
"Love doesn't exist," Sherlock gasped, and he finally looked up, wet grey eyes piercing calm blue.
"Doesn't it?" John asked, caressing a cheek with his right hand.
Sherlock just looked at him with fear.
"I don't really care whether it does or not," John said, and he landed a soft kiss on the curved lip.
And Sherlock knew that it was a horrible idea, that in the end everything would explode into a shattered ruin, but he didn't have the strength to stop himself. He found John's lips and pulled him closer to never let go.