What do you do when someone hands you a box marked "FRAGILE?" On the top of the box in giant lettering is "Please Handle With Care." Naturally, you are very careful with the box, making sure you have your legs beneath it when you gently lift it off the ground. You take every necessary measure to not rattle the contents inside the box and give special attention to making sure no outside influences come in contact with the box. You treat the box as if it were a little baby that needs protection.
Unfortunately, most tennis players are very fragile. Most tennis players are sensitive (including some of the best juniors in the country, college players, minor-league professionals, and pros for that matter). Little ripples cause their boat to sway out of control, derailing their oars dipping into the water. I equate tennis matches to a water fight in the pool between two children. Johnny splashes chlorine into Ben's face. Ben splashes chlorine into Johnny's face. This goes on for a few minutes until one starts to cry. Tennis is the same idea, who can take the stinging of chlorine in their eyes longer? Whoever is tougher usually wins, plain and simple.
How does one become less sensitive? I promise you if someone could be less sensitive, they would do it right now. Nobody likes to be called sensitive and soft. Everyone wants to be tough, strong, and brave. The best way to wrap your brain around this sensitivity/fragility issue to look at it from a different angle. The angle I am proposing is from a scientific point of view. Science has proven we have two sides to our brain- one that is logical (does all the planning, making rational decisions and so forth) and the other that is emotional (it has strong urges to react to things- happy or negative). The bad news for tennis players is the emotional side is far more powerful than the logical side.
Since tennis is a contest that is antagonistic in nature where two players are calling each others lines, emotions come into play. A normal person will give into their emotions causing their tennis to seesaw up and down like a rollercoaster. Very few players can actively control their emotions and nobody is ever fixed. Sometimes a parent or coach will say, "I think Johnny has fixed his attitude." Nobody is ever cured, its an ongoing battle between the logical and emotional sides of the brain where the logical side must dominate the emotional side. Like an alcoholic who has been dry for six months, the sudden urge to relapse is always looming in the background. One can never be trustworthy of the emotional side as it has an irrational mind of its own. It takes a very abnormal individual to be able to manage their emotions under stressful situations, usually it is innate and part of their genetic makeup.
If you want to stop watching the same movie over and over again in your losses, be aware of what it means to be a human being. Think about when you practice, you practice under very little stress and the muscles are relaxed. But if your emotions are a rollercoaster, your fine motor skills will be slightly off, thus causing errors and mental mistakes.
The most successful players are not fragile, but anti-fragile. Now imagine a box marked "ANTI-FRAGILE" and on the side in giant letters it says, "Please Throw Against a Concrete Wall." You pick the box up and throw it against the wall with all your might. You pick it up again and shake it violently. You kick it, you jump on top of it, you try to break it. Nothing happens. Nothing. This is a very robust box.
One could argue a tennis player deemed "ANTI-FRAGILE" takes it one step further. Shocks to the system make the player stronger. The toughest and least senstiive players are able to get stronger and tougher in stressful situations.