As someone who also juggles (literally and figuratively) a dozen hobbies, I call this learning by "teetering on the edge". It's not just about being curious. It's about constantly figuring out unorthodox ways of challenging the same skill.

You want to force yourself to the very precipice of uncomfortableness. This is an ongoing process since our brains are designed to ruthlessly optimize any skill that you are learning.

Let me give an actual specific example. When I was a teenager I became interested in learning the piano. I quickly found myself plateauing where sheet reading was concerned. In an effort to scale the difficulty up, I used to take the organ sheet music from our local church and try to play it on the fly on a piano. The challenge? There is an extra bottom staff representing the notes to be played on the pedals - thus you had to transpose that bottom staff up while you were playing and merge them together in a pianistic manner.

Another example? I used to play a LOT of Tetris for the NES. As soon as I could feel my internal system optimizing - I wrote a tiny little program that would use text-to-speech to read out random arithmetic problems that I would try to answer while playing. I remember the first time I tried this it felt like somebody had poured miracle-gro on the dendritic trees within my mind.