A fellow Shakuhachi player posted this on Facebook. I find this quite appropriate to consider when practicing.
In practicing alone, exercising the voice and singing, even though you may be all by yourself, in private, you should, all the same, think of yourself as appearing before exalted persons, and adopt
the proper attitude for a fully formal performance, and sing whatever
you’ve chosen that way. Maintain a formal posture, establish the
correct pitch from the start, and be resolute in both mind and body
that this is an appearance before a large and actual audience;
don’t for a minute think it’s just a private matter, but take a
vow in your heart, and sing as if it were an occasion of the greatest
importance. Once you have resolved your mind in this manner, then
your training will proceed correctly and no matter how great the
audience, you will not falter or suffer from stage fright; this is
a method whereby you may avoid blunders and misjudgments regarding the measure of your abilities.
As you train like this and study in the most comprehensive way, you should, as I said before, regard private practice or, for that matter, singing in any traveling performance off the beaten track, as if it were a formal performance before exalted persons; then, when you are actually called upon to do a command performance on an important occasion, you won’t be worried about your exalted audience, but instead have confidence in the power of mind you have cultivated in mastering the matter of your training; you will be able to regard the perceptions of a vast audience, with pristine confidence, as a single pair of eyes, and sing away, thinking – first pitch, second chi, third voice.
Noh master Zeami, from Fuugyokushuu