1. Appreciate the Progress and Achievements You Have Made
Sometimes in our quest for perfection, we forget to look back and appreciate the immense progress we've already made. Just as gratitude is associated with happiness and joy, appreciating all the small steps on the way to a goal helps ease our frustrations and gives us the encouragement we need to continue. Instead of beating yourself up for not mastering a piece of music, think about how far you've come and all the amazing things you can do. With students, try to remind them of how far they've come--"Remember last year when you struggled on a previous piece? Now that piece feels easy, and this new piece is hard, but by next year, I bet you'll look back on this piece and think about how easy it is!"
2. Try a New, Fun Piece
One of the things I like doing when I'm fed up with practicing is to play something fun and new. For me, that might mean playing through a violin version of the Lord of the Rings Soundtrack, or a few Irish fiddle tunes, or Renaissance ballads. The change of pace is refreshing, and often taking a break gives me a fresh perspective on the piece I struggled with.
3. Review an Old Favorite
When you're struggling with a new piece, sometimes it's nice to go back and review an old favorite. I often encourage my students to find a piece that they've previously mastered that has similar techniques to their new piece, and review it. It helps to build connections between pieces, and it gives them an ego boost to play a piece they've mastered. For me, I like to review techniques like scales and arpeggios when I get frustrated. It gives me a nice warm-up/break, since they're so familiar.
4. Take a Deep Breath
When we get frustrated, our bodies get tense and stressed out. Of course, unnatural tension often distorts our technique, so instead of getting better, we start playing worse. It's a downward spiral: frustration leads to tension, tension leads to more mistakes/worse tone, more mistakes lead to more frustration. To break the cycle, we need to stop, take a deep breath (or ten), and let go of the tension.
5. Remember that Struggle is a Critical Part of the Learning Process
Playing music isn't something that comes easily to most people, and even immense talents like Mozart spent years honing their skill. Evidence shows that we learn more when we struggle with a concept--mastery takes work. So instead of letting our struggles frustrate us, we should appreciate them as a sign that we're working hard enough to learn effectively.