"Ninety percent of my game is mental. It's my concentration that has gotten me this far. I won't even call a friend on the day of a match. I'm scared of disrupting my concentration. I don't allow any competition with tennis."

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It's not whether the glass is half empty or half full, it's who is pouring the water. The key in business and success at any endeavor is doing your best to control your destiny. You can't always do it, but you have to take every opportunity you can to be as prepared as-and ahead of-the competition as you possibly can be.

— Mark Cuban