No matter what happens when you play tennis, you need to react positively and get ready for the next point. I have heard this from many great coaches, the most important point is the next one. The thing about reacting positive is you become mentally tough after a while, because nothing can affect your game. Sports is 80% mental, never forget this, thats why you have to do whatever it takes to become mentally tough. Never let them see you sweat, as I have said before, the goal in tennis is to put your opponent in a mental state that they will give up. Always make this your main goal when playing a match, wear them down, then turn up the pressure. After that,the match is over. Action tip, when you lose a point say something positive to yourself, force yourself to use positive body-language. play with your strings, but never start the next point, until you have mentally recover. This is the one problem i see with players all the time, they don’t recover mentally before the next point. Do this over and over until it becomes a habit, you have to really focus on this part of your game to master it, put it is definitely worth it. Give it try and start mastering your emotion and winning more matches.