I’m sure you’ve heard the advice to “practice sections as slow as you need to to get it perfect.” My problem often is, usually there isn’t a spot on the metronome, no matter how slow or fast, that I can play to and get the song perfect. That may be similar to what you’re experiencing. I’m not sure any professional or teacher would recommend this, but in this situation, my “last resort” plan of attack to literally practice the section or song how I want to, without regard to its proper timing. This includes pausing to remember sections or make sure I finger them correctly, and is also a great opportunity to focus a little extra on my technique.
The struggle with trying to practice a song all the way through is that you’re on a clock. Every note must be in time. This is absolutely crucial to practice. However, I’ve found that often I need to take some extra “beginning steps” to even be able to practice with the metronome (I don’t have a healthy relationship with it, so take my advice with a grain of salt.)
Consider memorizing a passage or list of text. Let’s say you’re trying to recite the periodic table or the Presidents in order, or 100 digits of Pi. My guess is that your practice recitation wouldn’t come out conformed to a steady beat. It would be quite hard to do that without having already practiced that first - even if said beat you had to conform to were extremely slow. Rather, you would have parts of your recitation that come easily to memory, and parts that come slowly. By reciting with no “time feel”, you’re able to tell where these are and somehow, after much practice on your own clock, the entire recitation becomes more smooth.
This is because each time you ask your brain to retrieve that certain piece of information, it seems to simply become more “familiar” with the path it needs to travel to bring it forth. The road gets smoother; the directions seem to be more easily understood. The brain goes from “uhh… ce…sium… Barium… um, the next one starts with an L…” to “What comes after Barium? Lanthanum, of course! I’ve always known that.” Eventually, at your highest level of memorization, you’re able to recite from memory at any kind of rhythm you wish.
So it is with music. I wish that I could always practice things through, starting at some slow point on the metronome where I’m “perfect” and bringing my perfection up to speed. But sometimes, sadly, my “perfection” spot does not lie on a point on the metronome. It’s not actually perfect, because proper timing is part of playing the piece correctly. But, sacrificing that does allow me to hit the notes without as many mistakes.
Sometimes, you’ve got to laser focus on not just one measure or one section or one tricky ornament - sometimes, you’ve got to laser focus on one aspect of your playing itself.
Use with caution!
(P.S. I’ve been playing guitar 7 years and I still can’t play an arranged song perfectly without mistakes)
Also, are you playing from the tab? If so, I recommend you memorize the way the song sounds and move away from depending on tab as soon as possible. Once you start associating your hand motions with the sounds rather than the notes on the page, your “missed” notes will start sounding more intentional anyway. The most recent Picky Fingers Podcast involved a review of a recent EP the podcaster’s band produced. At the end of one song he completely missed the chord, but the whole band thought it sounded so good, they left it in the final cut.