It's also extremely nonlinear. I look back on my years of studying piano and the first 7 or so as a kid were basically screwing around compared to the next two, when there was this huge breakthrough. Then another couple years at that level until another huge breakthrough. It's funny, the first one was a breakthrough that came from a great teacher and was sort of a realization that music was way much more deep and interesting than I ever imagined. The second one was barely musical at all, it was just finding a super vibrant music community. If not for some random luck, mindshifts and social experiences like that, I would've quit a fraction of the way in.