I've been studying the piano for 10 months, mostly by myself, with a total of four lessons with a teacher. My piano story is in another thread and I won't recapitulate it here. My intention for this thread is to invite you to share all of the things you needed to learn about "how to learn piano" that you didn't know would be part of the process.
Here are some examples of skills I've been leaning that aren't in method books, but I think are critical skills that absolutely can be learned.
Maintain an effective balance between sensitivity and resilience. To perfect a piece, one must perceive and adjust many variables, which requires a fine sensitivity. But being very sensitive sometimes makes it hard to endure critique. So I think it requires work to balance sensitivity with resilience without allowing resilience to turn into defensive hardness and cynicism, which close the doors of learning. It's impossible to learn without first making mistakes, and owning up: "My best is not what I want it to be ... YET!" and embrace the terrific news - that there's something you can do about it! There are actions you can take! Hooray! I think to balance both toughness and sensitivity requires practice.
Maintain an effective balance between ego and humility. It is healthy ego that keeps us engaged in what is a very difficult endeavor. If we are not confident we can do it, engagement erodes and momentum dies. On the other hand, the ego must not take over such that we refuse to accept any influence. Pianism is an infinite subject; there is always something more to learn, and it's in one's best interests to accept the guidance of others rather than reinventing the wheel. Discernment is a critical skill that can be learned: What advice do I take, and from whom, and why? What advice do I ignore, and why? You've got to decide for yourself, because in the end, you're alone with your choices on the bench in an audition or performance, where the rubber meets the road.
Maintain an effective balance between consistency and flexibility. I can think of a lot of examples. We learn the piece on the page, exactly as written (or with changes) but we also practice recovering from failure. We show up on schedule to practice, or we wedge it between doing dishes and reading bedtime stories. We try a brand new thing because we saw a Molly Gebrian video and try to be consistent with our breaks too. And most importantly, I think, we practice keeping our mind open. I recently watched Ben Laude (Tonebase) take notes from Leon Fleischer on Beethoven's Pathetique, and it is always humbling seeing how Ben can (mostly) stay flexible on how to interpret a weighty piece that he has, no doubt!!!, played hundreds of times to achieve a consistency of tempo between passages!
Lastly, there is a skill to choosing which of your own thoughts to believe and which thoughts to discard as "not useful". If anyone thinks I say this too lightly, I will trot out my bona fides: I have a professional, medical diagnosis of obsessive compulsive disorder (OCD is probably not what you think it is), generalized anxiety disorder (GAD), complex post-traumatic stress disorder (cPTSD), and several of my family members have bipolar and autism spectrum disorders (for which I don't have diagnoses, but potato/potahto, you get the alphabet you get, and you don't get upsetπ). The one and only effective path through this morass to a meaningful, useful, and healthy life (for me) has been learning the skill of not believing every thought that pops into my head. It is a specific skill that I had to learn - to take a thought about myself, or a belief, turn it over in my "hands," poke it with a sharp stick, and make a decision about its usefulness and how to consciously respond.
I think developing control over your own thoughts and your own attention is the most important skill to learn, because our own unhelpful thoughts can be the highest, widest barrier between ourselves and maximum effectiveness at the piano bench.
To wrap up, in addition to the easily quantifiable skills we must learn as serious pianists (or in my case, a serious student!) - ones like sight-reading, articulation, dynamics, truly listening to develop our musicality, etc., there are mental skills (yes, learnable skills!!!) that are also required, because without those, we just can't be as effective at this wonderful and challenging endeavor of learning to play (and playing) the piano.
I would love to hear your thoughts, additions, and YES, even arguments against something I've said! My alphabet soup of health challenges does not mean to import any intellectual fragility. On the contrary. To overcome the challenges, I've had to learn the skill of resilience. It has only taken me 50 years! Imagine how much piano I can learn in the next 30 years if I keep it up!