"Falling is just like flying, except there's a more permanent destination."
Sherlock breathed in, smelt the smoke. He turned around to see Moriarty, one cigarette sticking out of his mouth, another in his extended hand. "A present for you, Sherlock. You might as well take it; you're going to die no matter what."
Sherlock thought about it, tried to resist, but Moriarty was right. With five minutes left to live, the smoking wouldn't kill him now. No, that would be Moriarty, coaxing him off the building. He could almost hear the rifles clicking as they were cleaned and loaded, waiting for the moment when their bullets would tear through his friends' bodies.
So, no, the cigarette wouldn't hurt him. The only reason he hesitated to take it at all was because it would mean giving in to Moriarty. That would hurt. But he really needed that cigarette. He took it out of Moriarty's hand and waited for Moriarty to light it. As he breathed in the smoke, a calm washed over him. Not calm enough, but now he could think.
Moriarty had snipers on Watson, Mrs. Hudson, and Lestrade. The only way to call them off was in Moriarty's head, and he would die before he gave that information up. Sherlock's panic grew again as he realized his only option, to do what Moriarty asked and jump. But if he was going to die, so was Moriarty. He spoke, rambling about the information in the villain's head, waiting for what was coming next. He smiled thinly as the bullet finally went through Moriarty's head. At least something went right today.
He could still hear Moriarty, though, talking inside his mind like he owned it. "You have to jump, you know. My death doesn't change that. In fact, now you have no other choice, Sherlock. Jump, and join me in hell."
Sherlock didn't want to listen to the voice inside his head, so he delayed it for as long as possible. His call-note to Watson only made him feel worse, but he had to. He took a breath in, his last breath ever, and stepped off.
John filled his mind on the way down, begging him to stop, to learn to fly, but it was too late. In that final split second before he hit the ground, he thought, not of John, but of Mycroft.
"Sorry, brother." And then there was nothing.