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The tennis world is constantly changing. What's true today may be wrong tomorrow. If you don't make progress, others will and you will be overtaken.

"Why The Grand Slam Is No Major Deal To Serena Williams' Coach". Interview with Mark Hodgkinson, www.espn.com. August 26, 2015.
The tennis world is constantly changing. What's true today may be wrong tomorrow. If you don't make progress, others will and you will be overtaken.