Don’t beat yourself up over missing a note or two… or ten. When you’re learning how to play an instrument like the guitar you have to be kind to yourself.
The truth is that it’s rare for even professionals to play an entire show, much less a song, from beginning to end without a little mistake. In many cases it’s mostly noticeable only to the performer and not the audience. In some cases it’s even noticeable to the audience. However, the show must go on. Most mistakes are forgiven because the show or song as a whole is what determines whether the listener enjoys it and not a little mistake. If you’re not okay with making a little mistake here or there, when you do make one, it can throw you off and quickly snowball out of control. You will start making even more mistakes. Keep a poker face and don’t stop playing.
I’m not suggesting that you should not strive to play all the “right” notes, just don’t sacrifice your enjoyment of playing music to fulfill a goal that is time consuming and offers less reward than more attainable goals. An example of a more rewarding and attainable goal is to add dynamics (shifting between loud and quiet). You could map out where you will get loud or quiet, or maybe your piece already has dynamics written in. This effect, changing volume, really adds another dimension and draws listener in. It’s also very expressive and can communicate emotions better than simply hitting “right notes.” It’s less frustrating to practice and enhances your overall sound.
Don’t start over from beginning just because you missed one note. It’s frustrating and you may never get through a whole piece if it’s even slightly above your skill level. Make a mental note where you need to improve but finish the piece. If mistakes seem to be random and pop up in different places each time, here’s what to do. Segment up a piece so that you can play each segment really well and practice each segment from beginning to end. Each segment should overlap, so connecting the segments takes less effort and time. After you segmented up the piece, have each segment well enough to play without stopping, then you can practice playing through the whole thing, with mistakes and all.
Having it in your mind that you must get through a whole piece with no mistakes is a huge pressure and is setting you up for frustration. Not that it can’t be done, but there are more important things that you should be practicing. Like bringing a piece to life with dynamics, timbre, articulation, vibrato, etc… Getting stuck solely trying to get only the pitches and rhythm 100% perfect is not only an inefficient way to practice, it leads to massive frustration, your worst enemy when learning the guitar. Besides, playing through a whole piece with no mistakes is not as rewarding or fun to listen to as someone really putting their heart into the music.
We as humans (assuming that you’re human) have qualities that resemble imperfection, so why should we expect our music to be perfect? Music is a reflection of our inner being, where there is inner conflict (in the mind) there is outer conflict (appears as mistakes). If we are at peace in the mind we make fewer mistakes. When we lose our peace of mind from making a mistake and not forgiving ourselves, we only end up making more mistakes.
In this “Age of Information” and technology we have the ability to create musical recordings free of mistakes. In fact we have come to expect that when we buy a studio album or listen to the radio. It’s unfair to compare yourself to studio recordings with all the editing, pitch correcting and the option to record hundreds of takes until you get that “perfect” take. Hearing live music is much different. You might catch a mistake or two, but little “forgivable” mistakes. Mistakes that don’t affect the overall integrity of the performance, but stuff we just don’t hear on modern studio recordings.
Think of Music as a living thing. Imagine a tree that may have a few dead leaves on it, but it’s still healthy. Aesthetically speaking a few dead leaves don’t detract from its beauty or your ability to appreciate the tree as a whole. The tree as a whole is healthy and vibrant despite the dead leaves. You climb the tree, risk your neck, probably get scraped, accidentally kill some insects, maybe get pooped on by a bird, and possibly damage the tree just to pluck all the dead leaves off the tree, but does it really look better? You just suffered, caused suffering and maybe even, by damaging the tree, made it look worse! Dead leaves will fall all by themselves. Just like mistakes will become less, the more you practice and the less you dwell on them. Perhaps my tree metaphor falls apart here, but the point is that doing something that frustrates you does not help, it only hurts. Another summation is that the life and beauty of a tree or song is not determined by a few little blemishes, there’s a bigger picture to consider.
If you’re a perfectionist, nothing wrong with it, just means you need to practice moving past your mistakes instead of getting stuck by them.