As you get older as a tennis player, you will eventually feel like you are not improving or not having fun! When this happens, start abiding by the "2 Step Rule."
 
Simply put, do not expect the ball to come to you. Instead, learn to move "2 steps" in the direction of the ball that is coming near you. What will stop you from improving or even getting invited to play will be your footwork. By the way, don't forget the biggest reasons you play are for the physical conditioning and secondly the social environment.
 
Try standing still on the court and look how far you can reach just by moving your arms without your feet. Remember that the racket is approximately 27 inches long, which is approximately the length of your arms. So, you have 54 inches of reach before you move your feet. By moving just 2 steps in every direction (forward, backward, left and right) you are bound to get better reaching more balls, have more people wanting to play with you and in general, be much happier and healthier. Now, stand on the court and move just 2 steps in every direction and you will see much more of your potential.
 
Remember it is a movement sport. So, don't give up on the ball until you have taken at least "2 steps!"
 
Good luck on the courts!