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The sword is a handle onto the Way of the world that is offering itself to you. If you are willful it will weigh a ton and wear you out. If you lose focus it will cut open your hand. Mindfulness keeps your mind on the blade; and if you are mindful you will not think about the future or past, there will be no blocks to the flow of Tao, and the Way of the world will flow through the sword and through you.