Thanks, lukediv!
I think I can truthfully say it has been the most difficult piece I've worked on, and frustratingly so, because it's chill, relaxed, and simple and pure on the surface. There have been many times when it felt like it would never solidify, but it's just such a beautiful piece, I knew I had to keep working on it.
There's something about the continuously wide traveling range of the left hand and the unique harmonies that make this piece very hard to learn for some reason. It's not like the straightforward arpeggio-based pulse of a Chopin Nocturne, for example. Every wave is different, and it's so easy to get mixed up. I feel like this would have been miles easy to learn as a teenager, before the brain starting trying to analyze everything.