Practice also putting the second serve in different locations on the court. When you practice against opponents take a few more risks on your second serve. This may cause you to double fault a little more and it may even cause you to lose to players that you might normally beat, but in the long run it will be beneficial. Raphael Wolfe Breathing and keeping your head down on the ball. Two very important things to remember when under pressure.
Breathing is very important when playing tennis, especially when things get tight.
As you stroke the ball try to use a steady breath release as opposed to a grunt. The problem with a grunt is that if your grunt is not executed at the exact moment of impact with the ball your timing will most likely be adversely effected. The timing of the grunt with the contact of the ball is the first thing that will fall apart when things get tight with a grunter. I try listen to this cue when I am playing against a grunter. With a breath release you are not dependent on perfect timing between breath release and contact with the ball.