One thing I forgot to mention is that when I reach that state of mu shin, all anxiety and worry fade away. It's like being truly in the moment where the only thing that matters is you and the sword...or whatever is most important to you at the time. It may sound cliche, but it's like the Force. The sword becomes alive and I can feel a resonance and energy in it. For the time I practice, noting else exists and I have no problems or pains.