The fear of losing while playing can motivate greatly, but most often negatively because it distracts and impedes optimal performance. Fear is a terrible focal point. It causes world-class tennis players who have spent a lifetime developing and perfecting skills to choke and double-fault with elbows of concrete.
Neuroscientists describe this event by explaining that, implicit movements ingrained with massive repetition and performed without conscious control are "short circuited" by fear and pushed into the explicit mind. When expert mindsets are reduced to beginner mindsets, performance is altered and most often compromised.
The problem is not a lack of focus, but too much focus. Fear causes the autonomic nervous system to activate, and while this response is managed without harm by some, for most players, it a disaster to the sequencing and timing of motor response. Simply stated, fear is a trigger to "paralysis by analysis."
The name for the concept that, if you are so scared of losing you may focus on that fear and you will be helped to concentrate on breathing, forget the score, play hard and go for everything is called "Cognitive Dissonance." This is a discomfort caused by holding conflicting ideas, beliefs or emotional reactions.
Overconfidence causes players to stray from what Billie Jean King describes as "being in the now." The best performers are highly-organized on the court and not distracted by a lack of humility that leads to complacency.
With my apologies to Joel Ross, who I highly respect, and his latest blog, I agree with President Franklin Roosevelt who said, "The only thing we have to fear is fear itself."