Sherlock has an abnormally cold body temperature, whereas John is abnormally hot. This really bothers Sherlock because now that him and John are close, he craves John's body heat. He feels warmer next to John, both physically and emotionally. This meant that he always wants to sleep extremely close to John, usually sharing a pillow with him instead of letting John be more towards the middle of the bed.
Which has not always been very…comfortable for John.
He is used to sleeping on a small bed, most commonly a cot, but sometimes he likes to just sprawl out on his own bed and not have any troubles.
Not when Sherlock's around. Sherlock will climb into bed and wrap his cold body around John, and John in turn would hold Sherlock close.
More than once, however, this hasn't worked out.
John began to get too hot with Sherlock directly next to him, so he scooted over.
And soon enough, John was trying to catch his balance on the edge of the bed.
And didn't succeed.
*Thud!*
"Ouch! Sherlock!"
"Mmmm?"
"Dammit, Sherlock! Scoot over!"
"Shush, John. I'm sleeping."
John picked up a pillow and hit Sherlock over the head with it. Sherlock jumped up.
"What was that for!"
"You pushed me off the bed!"
"I didn't mean to, John, come back-"
"I asked you to scoot over!"
Sherlock looked down at the bed, his outline about two feet from the edge of the bed, clearly not enough room for John.
"I'm sorry, John, I just-"
"No, I know, Sherlock. It's just, sometimes," John's voice was loud and strict, like he was scolding a little kid, "Sometimes I want my own space, do you understand? I know my life fucking revolves around you now, but-"
"I didn't know I was that much of a burden."
But he did. Sherlock had felt like a burden his entire life, except the moment he found out he was adopted and knew how much his mother loved him even though he wasn't really hers.
Sherlock looked sad. John's heart sank a little and he reached for Sherlock's face.
"No, Sherlock, that's not what-"
Sherlock stood up from the bed and grabbed the blanket that was on the edge of the bed. He wrapped it around his body and went to the door. Without looking at John, he said, "It's all right, John. I'll stay out of your way." He felt like all the warmth left his heart.
John laid on the bed and stared at the ceiling. He felt empty without Sherlock next to him, and he felt horrible for yelling at Sherlock. He turned sideways to lay on Sherlock's cold pillow. It smelled like him and even, somehow, felt like him.
On the couch, Sherlock was wrapped in his blanket and staring out the window. He was freezing, but he wanted to leave John alone. John hadn't yelled at him like that in a long time, and Sherlock felt bad for making John so angry. He never wanted to make John angry, he never wanted the fear that John was going to leave him. He loved John and he never wanted to be alone again.
For two hours, John laid awake in their bed. He didn't move for a while, trying to save the bit of bed that was warm, and he didn't want to make any noise to make Sherlock think he was awake.
John realized Sherlock must be freezing. Sherlock was abnormally cold blooded, and the heat downstairs wasn't on. He went downstairs to make sure Sherlock was all right.
Sherlock fell asleep after a while on the couch. He was tired and knew how to fall asleep without John because he'd slept alone for so many years before. He was wrapped in his blanket, trying to keep warm. John just stared at him for a minute or two. He could never look at Sherlock and not be in complete awe that this person was all his, and will only ever be his. He was so peaceful when asleep, and John thought he was most happiest when asleep, when his mind was at least partially turned off and he had no cares in the world.
"Sherlock, wake up."
"No."
"Why? Sherlock, baby, I'm sorry."
Something in Sherlock warmed up each time John used a term of endearment towards him. "I'm tired, John."
"I know, just let me apologize and I'll let you go back to sleep."
Sherlock opened his eyes and looked at John. John knelt next to the couch and laid his head on Sherlock's chest.
"I'm sorry, Sherlock. I'm sorry that I yelled. I just don't like falling off the bed. And I was tired and grouchy." he took Sherlock's face in his hands, "I don't want to spend any minute ever making you feel like you're a burden. I didn't mean that." John reached up and kissed Sherlock, trying to make him feel as special as possible.
John climbed under Sherlock's blanket and held him close. Sherlock's warmth went back to his heart.