Since Dr. Gebrian wrote a whole book about practicing, it would take me a month to boil it down into accurate talking points with footnotes to sources, so I'll just say that I'm noticing folks responding to this thread as though they're in an argument with one another. But every single idea here is examined in Learn Faster, Perform Better, but each thing in a different phase of studying a piece of music.
Try to make zero mistakes while learning and practicing.
While learning, focus on small chunks, and take small breaks (e.g., play the chunk slowly 3 times, rest for 10 seconds, and do that 3 times). There is a point of diminishing returns, so don't overdo it.
Despite your best efforts, you'll probably make some mistakes, so play correctly more often than incorrectly. If you make a mistake, slow down and play it correctly for some number of times that works for you (taking small breaks).
I watch a lot of YouTube. One of my favorite piano people is Tiffany Poon. She often shares clips of herself practicing. When she makes a mistake in a passage, she stops and repeats a small section around the mistake several times, then takes a break. Repeat. Ad nauseam.
(And this is just the "muscle memory" encoding. There's a bunch of other things to do to get the piece in best, most reliable shape.)
There's no rule mandating how many times is necessary to make sure you've played a spot correctly more times than you have played it incorrectly. So I'm guessing everyone gets to choose that for themselves. I'm not actually that rigorous about it. If I keep making the same error, I treat that differently than some weird error that I haven't seen before. I think the whole point of this is just to change the Big Picture of what practice looks like, not to leave us feeling nibbled to death by ducks.
Lots of people are agreeing on basically the same things. Don't start at the beginning of the piece every time you sit down to practice. Don't stop when you make a mistake and only correct it once before moving on. Don't keep pausing in the same spot, because you might bake the pause into the cake by accident. Have a plan. Figure out what's going wrong instead of mindlessly repeating and hoping for the best. And so on. It's not a mystery or an arcane ritual, where you just grind yourself into the ground with hours and hours of hopeful but unfocused playing. (But again, if you hate the very thought of doing things this way, just don't. There are no practice police. Do it your way and have fun. Life is short.)
I think I know why pianists love to get into these nibbling conversations, though. Playing piano is hard, and takes a lot of effort, and our loved ones get bored of listening to us slice and dice and moan and quibble, so we torture each other instead.
My practice is still kinda chaotic, but I'm trying to clean it up so I can work less and get better results, so I'll be less boring to my loved ones.
😁