Many of us tend to warm-up for a match the same way. We start on the service line and tap or rally the ball back and forth for a few minutes. Then we move back to the baseline and hit full length ground strokes for a few minutes. Then one of us moves up to the net, while the other player stays on the baseline. After a few volleys they will ask for a few overheads. Next the players switch court positions, and this allows the other player to hit their volleys and overheads. Lastly, we hit a few serves and then the match starts. This is a fairly standard pre-match ritual.
 
However, next time you go out to practice try this! Still warm-up a few minutes on the service line to service "tapping warmup." Then with both players back for a few minutes, go to every ball and position yourself like you are in the match. If the shots are deep start back. If you receive a short ball follow it to the net. Hit your approach shot, net volleys, overheads and normal volleys. However, do not try to put the ball away. Keep it a reasonable, controllable pace and hit it near your partner. When the ball is out of play, go to the baseline and start a new point.
 
This way you will practice the positions you must master in the real match. Many times you will see two players, while just hitting, allow all the short balls to bounce 2-3 times before they return it. This is a very bad habit. Move in to get the ball on the first bounce and move to the net to continue the rally. Soon, you will have no fear of being drawn to the net. Also, you will get used to your opponent being anywhere on the court and not just on the baseline.
 
Remember, as soon as your opponent knows that you hate to come in, they will use that against you. Please try this the next time you play or practice. You will find that your movement is better when you practice and it will make you a much better completive player.
 
Good luck on the courts!