Many times, a student of mine will look very good during a very controlled lesson. Why?
 
Because I am controlling the ball feed to make the student feel successful. The same place and speed. Not like a real match.
 
Everything can go wrong in a real match because you always seem rushed, off balanced and clueless. Why? You are only reacting to what the opponent is doing! You are not anticipating.
 
Try this! Start thinking about where your opponent's shot is going to land, in general. Then try to go to that spot where you think the ball will bounce before your opponent's shot crosses their service line.
 
When you are at the net, start thinking about when your opponent's shot will intersect the net and start moving to that point before your opponent's shot crosses their service line. This way you will feel more in charge. You will be anticipating and not just being controlled by your opponent.
 
Good luck on the courts!