Kendo derives from the sword fighting, which is a life and death circumstance. Many Samurai studied Zen Buddhism, as it was a very good way of clearing distractions in the mind and helping with creating a skillful swordsman. In Kendo we cannot promote religion as the reason for becoming more skillful. The effects of properly preparing oneself are very important however. The correct way to sit in Seiza is as follows.
Breathing is very important.
Breath through the nose. Breath out quickly but not unnaturally and start again with the inward breath. This breathing will help give focus and concentration on the Ki center or Tanden . By setting ones mind one can focus during Kendo on the opponents weaknesses by eliminating ones own weaknesses. This state of mind is what Taguchi Sensei says makes a perfect Kamae .