We're human, and life happens.
Suddenly, your dog ate your music, or the contact lens sits askew, or you couldn't sleep more than three hours the night before the concert because you had a bad cough (and we know how difficult it is to fall asleep when you're coughing like a dog with a hairball).
Or the promoter is 90 minutes late to pick you and your harpsichord up with her car, although, horror of horrors, now you don't even fit in the passenger's seat anymore and you have to travel to the venue by public transport, good grief, and you get there with roughly 30 minutes to set up, tune the instrument and rehearse with the singer (that happened to me once, for example).
Yes, and you get there, and your heart is racing like mad (not so good), or you're in a bad mood (even worse), or you're on your last legs (awful).
And your whole body is feeling completely different, and your perception, which is subjective anyway, has been distorted in a completely new and inscrutable way.
And it becomes this huge task to access your habitual way of playing. (Especially when you're in a bad mood.)
And then what?
Because, the concert starts, like, in a moment!
How is your playing going to be? Which feeling can you rely on now?
In such cases it's useful to know what will center you. And then, to try introducing changes.
Once something favourable happens, even if it's very little, the spiral opens in the beneficial direction. And then, you feel more in contact, more openness in the body, and in the optimal case you can come alive on stage and play how you're used to, in spite of the dog and the cough and everything else.
We often think that the knowledge of musical movement will interfere with our feeling of it. But the opposite is the case.
Knowledge is absolutely essential for exact those situations.
For the knowledge to be available and not disturb the feeling for the instrument, it is to be trained, so it can flow into our experience, for example during practice.
And this can be the principal aim of practice itself: to unite the conscious with the unconscious. One without the other is fruitless.
When we acquire new tools through deliberate practice, we're in the position to turn an adverse situation into a favourable one, in a matter of seconds.
That may happen in front of the listeners, too.
Anytime is a good time.