well, don't underestimate the mental work, but still, i don't think you would gain 4 inches out of it, prob 1-2 inches.

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"Look me in the eye. It's ok if you're scared. So am I. But we're scared for different reasons. I'm scared of what I won't become, and you're scared of what I could become. Look at me. I won't let myself end where I started. I won't let myself finish where I began. Look me in the eyes. I have something more important more courage. I have patience. I will become what I know I am."
-- Michael Jordan