Molly Gebrian says that if you want to fix a mistake in a passage, and you practise it playing both correctly and incorrectly, you reinforce both the good and the bad neural pathway for playing this passage. Therefore you should play it correctly ten times in a row.
When I first read this, I thought, never in my life. When fixing a mistake in a passage, I have a hard time playing it correctly even five times in a row. I use a more friendly method: whenever I play it correctly, I move a button to a new place, when I play it incorrectly, I move the button back, and in the end, I need to have five buttons at the new place. (I hope you understand.)
But I realise now that this reinforces both the correct and the incorrect playing.
However, with Molly's method, the passages are much shorter. Instead of playing a full passage, I play just a couple of notes before the note that needs to be fixed, and then, following her instructions, I stop on this note that I now play correctly. And with this very short passage, it is suddenly fully possible to play it correctly ten times in a row. When I do this, it really feels like I am dredging out a canal in my head leading to the correct note. And there is a new kind of certainty when I play the whole passage.
Not that it is always enough though. Sometimes I can only play the short passage slowly. So I put my metronome on a low number, play it correctly ten times in a row, do something else, then put my metronome a bit higher, and play it correctly ten times in a row once again. 😊