Answering my own question. π
Unfortunately, I find that I fall back into old practice habits, and practise mistakes...
I am working on one of my pieces and I felt I was making so little progress, and of course, I started to push. I could barely play the piece at mm 36 so I thought I would play the whole piece at 40. Guess how that worked out?
But yesterday I realised I was on a road to nowhere. So I restarted, chose random passages of four measures that I could play however slowly as I needed, as long as I played them correctly. In case I made a mistake anyway, I practised the correct note five times.
This was such a relief! Gradually, I increased to passages of five and then six measures, I took my metronome again and played the passage at 30, then 35, then 40, and then once again at 30, then 35, then 40 again. Today, I felt I could even add mm 45 to that sequence. Tomorrow I'll continue working with the random passages, and the day after tomorrow, I'll take a day off.
However, another piece I am learning is not suitable for Molly's schedule, at least not now. The first long phrase of the piece shows the main theme of the piece, without any embellishments, and I need to learn how to play that phrase before I can start learning the other phrases.