IMy advice: play pieces that seem to be really hard. It can be frustrating, but it sure as hell isn't as boring as Czerny or Bach's inventions.
Another one trying to wind me up
Bach's Inventions boring ???? They are among the very best study pieces there are, and musically so high above anything Czerny wrote that one should not even use the two names in one sentence. If anything is boring, it's Czerny's endless roulades of notes. Maybe not boring to the fingers, but just to the mind.
Having said this, I used to think the Inventions, and Bach in general, were boring for a long time... I dutifully trundled through them because it is was what my teacher told me to do, without much liking them or even seeing the point. Then at one stage, can't remember when exactly, Bach hit me like a ton of bricks. It will happen to you. There is no getting away from old JS
You advice is dead wrong though. Always playing pieces just outside your technical reach it tempting (used to do that a lot, too) and surely it is exciting. But I find, having wised up some, that playing the things you can
play, and try do them really
well, does just as much, if not more, for your technique and musicality.