In the diagrams above, the white "X" represents the placement of the ball machine and the yellow circle represents the contact point (more or less). The blue line is the path of the ball FROM the ball machine; the red lines are the paths of the ball FROM you. Instead of setting up the ball machine in the MIDDLE of the court, place it off-center (WAY off-center) and practice changing the direction of the ball. Rather than doing side-to-sides for 7 minutes and then quitting (because you're not used to hitting 300 balls in a row), practice hitting from a set location while keeping "light" feet...learn the "dance" steps immediately preceding the contact; hit and recover (or, like boxing, "stick and move"). Changing the direction of the ball is usually where all the unforced errors in tennis take place. So reduce the likelihood of mistakes by learning how to adjust for every angle. That is, how to hit a cross-court from a down-the-line; down- the-line from a cross-court; or a sharper cross-court from a cross-court. Again, keep your feet moving and groove your strokes (to the point where they're "in your blood"; AUTOMATIC) so that they don't break down under pressure. Supplement your lessons with ball machine training since, it's not only important to learn a good shot (something that lessons are intended to accomplish) but also to FORGET the bad strokes. To use an analogy, tennis is a lot like sculpting a statue: you have to do the hard chiseling and hammering work; the master (tennis pro) is the one who helps you bring out the details with the fine sandpaper...but then it's back to the chiseling and hammering work. This is YOUR project, not your coach's, so make sure that you take ownership of it.