What is your game plan for improving the way you play?  Do 
you take plenty of lessons?  Have you been to tennis camp?  
Do you watch all the tennis you can get on television?  
Although those things obviously help, many players neglect 
what I feel is one of the most important aspects of 
improving - competition.
Have you ever played in a tournament against someone that 
looked like a professional in the warm-up but completely 
fell apart in match play?  It happens all the time.  
These players feel comfortable until it is time to actually 
keep score and since they are in that situation only in 
tournament matches they may not be used to the pressure.  
Playing in a tournament can be great for your game and 
I've watched players of all levels improve after learning 
their real strengths and weaknesses in tournament play.  
Playing actual matches puts a certain amount of pressure 
on you that just can't be replicated in a lesson. 
 
If you are a tournament or team player I think it is 
imperative that you play matches to supplement your 
lessons if you want to really improve.  It's like doing 
your homework in school - you've been taught a technique 
or style and you need to put it to the test in some sort 
of competition.  Players may feel a false sense of 
security if they hit well in lessons but never use their 
game before the competition.
An example would be someone that can get in 10 out of 10 
first serves during a lesson but they habitually double 
fault in match play.  You have to learn to carry your 
lesson game to the actual match and the more you compete 
the sooner that will be.  I realize that not all teaching 
professionals will agree with me.  In fact I know that 
some players playing on tour have been advised to work on 
their strokes over a certain period of time without 
competing.  This philosophy does have some merit in that 
you might want to make sure that your game is completely 
sound before attacking the tournament circuit.  However, 
I see players that are competing in match play, 
tournaments, team tennis, etc. improve at a much faster 
rate than those who do not.
Just try my theory for a few weeks.  Double the amount of 
match play you have now if that is possible.  Many people 
use their lessons as their only form of practice.  Try 
adding just a match per week.  I bet you will find that 
not only will you improve faster but also you will learn 
your strengths and weaknesses better and get more out of 
your lessons.