Sherlock used to think that maybe people could fly, and nobody had ever really tried before. So, one day he found a ladder in the garden shed behind the house and climbed up onto the roof. He walked to the other side of the roof and looked down at the gravel driveway, with the sloping green lawn beyond it. He took a deep breath, then threw himself forward. For one heartrendingly wonderful moment he hovered in the air, before strong arms secured around his middle and Mycroft tugged him back onto the roof, cursing under his breath.
...
Sherlock had since deleted the memory, but Mycroft couldn't. He sat at his desk, staring blankly down at his papers and remembering how he had thought for a split second, as his younger brother jumped from the edge of the roof, that maybe- just maybe- things would be better if he let Sherlock fall. But Sherlock had grown older and forgotten, and he was doing good things. Sherlock was on the verge of falling in a whole new way, and there was nothing Mycroft could do about it this time.