Confidence in piano starts with you.
To apply it in practice, you have to own the piece and know that you deserve to play it.
I'm currently practicing Chopin Fantasie in F minor Op.49 and can play it slowly from memory. Like any other virtuoso piece, you have to put in the work to get it up to speed.
The lesson is - what other people think about your performance is none of your business.
I've got a blog post on my site about this. I share what I've learned as a piano student, among other things.
I can say that even just posting videos of myself on the audition forum can be nerve racking and can be one of the hardest tasks I'll ever do. If I continue to care about what other members think of my performance, I'll never get better. You can go to the audition room and watch my playing of Liszt Transcendental Etude no.10. I don't care what people think about it because I'm after constructive criticism. You know what? I finally come to realization that the Liszt transcendental etude no.10 was too difficult for me to handle way before I even posted the video in the audition room. Because of how horribly I played Liszt Transcendental Etude No.10 (and I still do

), I began to lose confidence in myself with other pieces. Then I felt traumatized to play other virtuoso pieces since if I play Liszt TE 10 badly, then I'll play play everything else badly. Another feeling that I get is that people will think that I will always play piano horribly because of the way I played Liszt TE 10. You don't want to carry this burden around your whole life.
You play the piano from your heart and you want to share it, that's why play it.
@nyiregyhazi - If a student wants to play a piece you believe they're not ready for, only they can come to realization that they're not ready for it. What you do as a teacher is tell them this is how you learn it, and then they learn it on their own. Like me, I wanted to learn Liszt TE 10, but my teacher taught me no9 instead. Anyway, what this has taught me is that a student will come to realization that they're not ready for a piece after they have it memorized and they've tried everything they can think of. I've exhausted all the possibilities of what I can do with Liszt TE 10, and I came to realization that I'm still not ready for it, so I leave it and move on to something else. Let's face it, you don't want to work on ONE piece for 5 years while you can learn other pieces.
Same thing with La Campanella, I played it in a piano workshop, the teacher said I wasn't ready for it, then I realized why, but watching Yundi Li play, I had to find a way to learn it. He simply blows me away and I had to watch that performance 20 times per day before I could turn the PC off. I came back to it a lot of times, then I came across Czerny Study Op299/22 (study in repeated notes) and that solved one major problem I had with La Campanella.
I continued learning La Campanella, students said it was too hard for me, then months later, I blew them out of the water. I play in front of that same teacher who said I wasn't ready for it, and he was surprised by how seriously I took my piano playing. Still can't believe I tripped on that Contrary chromatic octave part in my end of year recital, it's the only time I ever slipped that part.
If you're a teacher helping a student gain confidence or if you're a pianist who wants more confidence, it's all about you having power and you own your own power, not someone else.
Another way to get pianistic confidence is to post recordings of yourself in the audition room here in the forum for feedback. The constructive criticism here is all part of your growth.
If you play a hard piece, you have to know that you deserve to play that piece and that you have what it takes to play it. You'll have a much easier time accepting feedback from other members and you know that it's all part of your development as a pianist and as a person.
Just remember - What other people think about your performance is none of your business.
Hope this helps.
