Many players can be taught to hit the ball correctly and look good doing it. However, many of those players never attain a high level of competency. In general, they do not "learn how to win."
When working with a player that is in a "rut," many times explaining to them how to "press" can send their game upward. I consider "pressing" as the ability of a player to always move forward to the ball. Most players wait for the ball to come to them or fall backwards while hitting the ball. These two habits allow a player to have a large, detrimental backswing and to not use their own natural body mass to absorb and hit the ball. By moving forward you will naturally take a smaller backswing, be able to keep the ball lower and better direct the ball.
Remember, good things happen when you move "forward." It is not necessary to move forward fast or to take large steps. You can accomplish good result by taking small fluid "baby" steps toward the ball. Never allow the ball to come to you. Always take that extra time that you are waiting for the ball to improve your position to go toward the ball. Do this on all your shots.
Remember, wherever you are when your opponent hits the ball, you should not be there when you contact the ball. Go to the ball. Press or be depressed.
Good luck on the courts!