Some days are bad. Downright awful. You pick up your flute and it sounds like crap. And you think, how could I have sounded SO GOOD yesterday, and today sound like I've NEVER TOUCHED A FLUTE IN MY LIFE???!
The great (and possibly depressing) news is that you are not alone! We all have these days. Even after 30 years of playing, I have them. And I have ways to survive them!
Step 1: Take a deep breath.
You might not be setting the world on fire today. That's ok. Take a deep breath. Check your posture. Check your mental state. Are you holding tension, anger, frustration? Do a little 3 minute meditation to reset your innards. If you need help, I love the Headspace app for this - short little resets that you can do any time.
Step 2: Identify what isn't working.
What isn't working for you today? Are you struggling with tone? Even technique? Control?
Step 3: Break that element down.
Having a bad tone day? Start on a B, or another short-tube note. Play just the B. Explore all the textures of the B. Is it fuzzy? Clear? Edgy? Soft? Smooth? Lumpy? Nothing exists for you but the B. When you're done with being the B, be the B-flat. Use it as a meditative exercise - you're just observing, not trying to change a thing.
Having a frustrating technique day? Pick one note in the passage that's getting to you. Play it on its own. Love it. Add the note after. Put your entire consciousness into that switch. Play it as slowly as you possibly can. Listen for what's happening in the switch. Observe, without getting emotionally involved. When it is as clean as you want it to be, add another note. If it isn't, play it some more. SLOWLY. Be forgiving of other elements that are involved - if this is an exercise in clean switches, don't worry about tone or dynamics or tuning or or or right now. The switch is All.
Exist on the lowest possible plane of flute playing. Feel the vibrations of the instrument under your fingers, in your ribs, reflecting against your soft palate. The idea is to just be - you're not trying to fix it, just to observe what's going on.
Step 4: Back off.
If focusing on the tiny details isn't doing it for you, step away from the instrument. Listen to a recording that you love, one that inspires you. Listen for all of the things that make the recording work for you, and internalize how it would feel to play that way. Sing along. Try memorizing the melody. Hear the lines in the other parts that go along with yours. Exist inside the recording.
Step 5: Try again tomorrow.
Bad practice days rarely last for more than 24 hours, so give it a break and come back to it with a fresh heart and mind.
Best of luck and may tomorrow be better!