"The difference between competing at 100% intensity and 95% intensity is virtually indistinguishable except that at 100% you win and at 95% you lose. [Why?] [Because] the difference between winning and losing is a surprising few points. In a close set, the winner only wins an average of 4 more points that the loser."
-Allen Fox, Ph.D.
Tennis: Winning the Mental Mental Match, (Kearney, NE: Morris Pub., 2010), Chapter 10, Page 111.