Breathing in your natural rhythm is important to stay physically and mentally balanced (meaning you shouldn't alter it), but nothing keeps you from using it to accelerate your writing. This exercise, which belongs to the Air element, is all about that.
Write Breathing is fun, and you can do it almost anytime and anywhere. You can use pen and paper, a computer and even your smartphone for it. You can do it at your desk, in your favourite café, or while on the move by train, bus or plane (maybe even spaceship).
I would recommend it as a motivational exercise for days of self-doubt, anxiety and sadness. However, you can also use it to break in the door to your voice. It's great at that and carries a lot of punch.