Yesterday was the day I have every week when it seems like I can't play any of my piano lesson. It's always frustrating because the day before, I had played all of my songs fine--maybe not quite up to tempo, and a couple of minor mistakes, but I could tell I was getting there.
The first day after my lesson, I'm playing with close attention, concentrating on reading the notes and playing them. I play very slowly, and go through the difficult parts by themselves a couple of extra times. I practice at least twice a day, each time for a minimum of 15 minutes; often it's more like half an hour three times a day, because I'm having so much fun learning piano. Over the next couple of days I start to play more confidently and with more pleasure than concentration.
But there's always the fourth or fifth day, when it seems like I fell apart: many wrong notes, hesitation before I play the next bar, and frustration. I push on, plodding through my minimum practice sessions. My goal is not to stop practicing any particular song until I have played it correctly at least once and preferably three times, but on the fourth or fifth day most of my practice sessions end with a song I have made so many mistakes on, I'm too tired to go on. I've even wondered whether I can do it at all, whether I have any ability to learn to play this instrument and make the notes into music for my enjoyment.
The only way I can handle the frustration is to remember that this has happened every week. I have to trust my process and keep practicing. Sometimes I slow everything back down, or practice just the hardest things for a few minutes. I know a big part of what has happened is that I got overconfident and stopped *reading* the music while I played, and I haven't actually memorized these songs yet, I still need to pay attention while I'm playing. I also tend to focus on what I'm playing with my left hand, and of course I lose track of my right hand work when that happens. But if I keep practicing through the rough spot, on the sixth day the effort pays off: not only am I playing better, but with ease instead of struggle.
My process isn't the same for everything I've learned, and discovering it usually takes more time than this. Trusting a process also takes time, but it's the only way to improve, so I do. Some kinds of learning I have to take a break from--a few days or weeks to let my new knowledge integrate into how I think and react and make decisions. Other kinds I need to keep making a regular, repeated effort to learn, to practice a skill and remember the tricks of performing it.
Take time to discover and trust your process for learning or doing anything important to you. Observe your patterns and use them to your advantage.