For performers of any instrument, a daily practice of a conscious resting position such as Shivasana (Corpse Pose from Yoga) or Constructive Rest (Alexander Technique) encourages a vital awareness of the whole self. Such a practice supports healthy use of the self while practicing your instrument.
I recommend a 3-5 minute lie-down just before practicing each day for a week. (You can do longer, but if you are impatient like me, a 3 minute true rest is better than a 10 minute impatient one!)
You can lie on a carpet or other padded surface, preferably not a bed, since it suggests sleep.
I prefer constructive rest to Shivasana, since it's a bit more specific and tailored to match the body poised in a standing position. (for a standard Alexander description, go to constructive rest, which has a pdf you can print out.)
The goal of this practice is conscious, intentional rest, not a nap!
Constructive Rest requires a few books under your head, to prevent craning it, enough so your eyes are point straight up to the ceiling.
1- Put an inch or two of books where your head will go, and test the distance by lying down with feet flat on the floor, knees bent.
(This next two steps are not required, but are helpful to elongate the back. You can also just lie down to rest your head on the book and go to step 4.)
2- Now roll up to seated with your feet flat on the floor, more than hip width apart. (You can also put your legs up on a chair as in the photo here)
3- Curl your head forward to your knees and, holding hands to backs of legs, SLOWLY roll back until your head can release to the books. Your legs may roll up as you roll back, or they may stay on the floor. Either way, you will feel a little work in your abdomen as you roll back. The purpose of the roll is to unwind your back to a nice, long resting position.
4- Hands can unfold to the floor at your sides or lie on your belly, whichever is most comfortable.
(You may adjust your feet position so your legs can balance so as not to flop either in or out. You may have to use a tiny bit of control to keep them there. That's okay. This is not as much about relaxation as it is active rest.)
5- Eyes remain open. You can focus on a point on the ceiling.
6- Allow your breathing to settle, and begin to notice the out breaths. I like to let myself yawn several times to get started. On each out-breath, allow your feet, hips, back, neck and head to sink a bit heavier. Keep that heaviness on the next inhale, and continue deeper on the next release of air. (notice I don't call it exhale, which implies pushing)
I imagine there is air in my arms and legs, and with each exhale, I let the air flow out of them.
Let the ends of each release of air to extend several seconds. You are in fact still exhaling, extremely slowly. This point is the most important in this practice, since it affirms a very neutral, open position for your body, full of potential.
Let your hands go, notice them releasing, let each finger go, until there is only a vibrant openness in them.
7- On an exhale, imagine playing a simple scale on your instrument. Take time to imagine this scale several times as you continue to be conscious of the resting energy of your body.
8- When you are ready, roll over to one side and slowly get up, keeping openness in your body along with the virtual scale. Then play. Notice what changes or tenses unnecessarily. Arms? Hands? Neck? Hips? Back?