Tune your guitar or any string instrument to 432 Hz instead of 440 Hz. The prior is a much more natural frequency for biological systems and will help relax the body. 440 Hz has been shown to be disruptive to biological systems, particularly our brain. Try it out if you're a musician and see if you notice a difference in how your audience reacts to your music, or even if it changes how you feel. Being slightly flat, I found that I could hit those high notes that would usually crack my voice.
