Mental training can be over-looked in racquetball.
First, remember, all the mental training in the world will do you no good if you do not have a good forehand or backhand so do not confuse mental training with the physical demands of racquetball.
Next, as part of your regiment, you should add some visualization. Here is a simple exercise that we learned out at the Olympic Training Center years ago-put a dot on a racquetball, hold the ball up and stare at the dot. Do not let a thought come into your mind, but focus on the dot. World class athletes can do this for minutes at a time. You will be hard pressed to (as I am) to get beyond 10 seconds.
Another tip is to imagine your match, shots, and use as many of your senses as possible. You can even record your voice and use the first person, and mentally practice.
Focus hard for practice matches to get used to it and you will see results. I believe it has to be practiced to be effective in a tournament. Rehearse and you might be surprised with the results!