"Frustration is the first step towards improvement. I have no incentive to improve if I'm content with what I can do and if I'm completely satisfied with my pace, distance and form as a runner. It's only when I face frustration and use it to fuel my dedication that I feel myself moving forwards."
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Source : John Bingham (2002). “No Need for Speed: A Beginner's Guide to the Joy of Running”, p.105, Rodale