The three weeks had a shape.
He had planned them the way he planned everything that mattered — with the specific architecture of someone who understood that intensity without structure produced exhaustion rather than progress, and that the difference between the two was not effort but design. Six hours daily, after the last class, through to midnight. But the six hours were not uniform — the first two were always technique, the specific precise repetitive work that built the physical grammar of the thing they were practicing. The middle two were application, which was where the technique met resistance and either held or didn't. The final two were pressure — simulated, structured, the specific conditions that would be closest to what Harry would actually face.
The first week was the hardest.
Not because the magic was difficult — though it was — but because the group was finding out what six hours actually meant. The theoretical commitment made on the train and the practical reality of being in the Room of Requirements at half past eleven on a Wednesday having been there since half past five were meaningfully different experiences, and the gap between them required adjustment.
Ginny adjusted fastest. She had the specific physical resilience of someone who had been flying competitively since she could reach a broom and whose baseline for what her body could be asked to do was calibrated higher than most of her age group. She made mistakes in the first week and corrected them with the specific efficiency of someone who disliked making the same mistake twice more than they disliked making mistakes generally.
Luna adjusted differently — not faster or slower, but sideways, which was how Luna adjusted to most things. The stealth work suited her in a way that was not immediately obvious but became apparent by the third day: she had an extraordinary natural stillness, the quality of someone whose default relationship with a room was observational rather than participatory, and the scent masking and heat masking charms built on a foundation that was already partially there.
Neville struggled in the first week and did not hide that he struggled, which Ron had learned to recognize as one of Neville's more valuable qualities. He asked specific questions. He went back to the parts that hadn't worked and worked them again without requiring encouragement. By the end of the first week he was not the fastest or the most precise but he was the most consistent, which was a different kind of useful and in some contexts more valuable.
Hermione was technically excellent from the start, which meant her challenge was not the technique but the speed — the gap between knowing how to do something and being able to do it under pressure without thinking about knowing how. This was the gap Ron had identified in October. The three weeks narrowed it considerably. By the second week she was casting the Disillusionment silently and it was holding under simulated resistance, which meant the thinking was no longer getting in the way.
Harry was the main work.
Not because he was the weakest — he wasn't, his raw magical ability was extraordinary and had always been, the specific quality of someone whose power was not the limiting factor and had never been. The challenge with Harry was precision under emotional load. He performed excellently in the technique sessions. He performed excellently in the application sessions. The pressure sessions, which Ron had designed to include conditions as close to a frightened dragon and a hostile arena as the Room of Requirements could produce, revealed the specific thing that real danger did to Harry Potter's spell work: it made it large and fast and slightly imprecise, which was the pattern of someone who had survived years of situations where large and fast had been sufficient and precise had been optional.
It would not be sufficient here.
'Smaller,' Ron said, on the fourth evening, when Harry had produced a Disillusionment that had worked but had flickered at the edges in a way that a dragon with the sensory capacity of a Hungarian Horntail would register. 'Not less powerful. Smaller. The power is fine. The intention needs to be tighter.'
'I know,' Harry said, with the quality of someone who had been told this and understood it intellectually and was discovering that intellectual understanding was not the same as having the body know it.
'Again,' Ron said.
They ran it again. And again. And on the seventh attempt of that session it landed the way it needed to land — clean, tight, the Disillusionment settling over Harry like a second skin rather than a cloth thrown over a shape, and Harry himself going still in the specific way he went still when something had worked properly and he knew it.
Ron looked at where Harry was and felt the specific quality of satisfaction that came from watching someone find something through the work rather than being handed it.
'That,' Ron said. 'Every time.'
'Every time,' Harry said, from the air where he was standing.