Summary: Merlin had always known he would never make a healer.
Thank you mods for extending the deadline so I had time to get this done and betaed! Very much appreciated, guys.
Merlin had always known he'd never make a healer. Not for want of trying, however; he had read all - well, some - of the books Gaius had given him which detailed the healing properties of various plants and he'd watched Gaius stew said plants into tinctures and salves which looked exactly as the book said they were supposed to and did exactly what the book said they should do. Somehow, though, when Merlin tried, it all went horribly wrong. He had no problems identifying the plants so the problem had to be in the preparation and stewing stage. The salves he made were always lumpy, the tinctures were never the right colour and he had yet to make one that Gaius would allow him to test on anyone.
He had less trouble with the things Arthur wanted him to learn - all the odd bits of first aid that might come in handy on the battlefield. Merlin didn't really want to think about why that was, unless the explanation was that Gaius's scorn and mockery was not followed by the threat of sword practice. He made the mistake of mentioning this to Gaius. This got him a look which was far more knowing than Merlin was really happy with, and resulted in him having to clean the leech tank after every unsuccessful lesson.
The first time he needed to make a salve for Arthur, it was perfect. He didn't tell Gaius.