Players are often caught out of position, leading to the opponent hitting an easy winner to an open part of the table as you lunge for the ball. But did he really force you out of position?
For example, suppose the opponent finds a chance to hit an angled ball to your wide forehand. You run it down, but before you can get back into position, your opponent has blocked a winner to your wide backhand, and you can only wave at the ball and say, "Nice tactic." But did he really force you out of position, or did you allow it?
Most often, when the above happens, it's not really because of what the opponent did, but because of one of two things you didn't do.
First, were you really in position to cover the forehand on the first shot there? Often a player isn't positioned well, and so when the ball goes the forehand (in this example), he gets a late start, and so is already almost lunging for the ball. Result? Even if you make the return, your momentum keeps you from making a quick return back into position, leaving your wide backhand open.
Second, while making the return from the forehand side - key word is while, not after - were you pushing yourself back into position with your right leg (for righties) so that you'd follow through back to the table? Many players finish their stroke, including their follow-through, and then start their return to position. Instead, returning to the table should be part of the follow-through.
If you fix these two problems, then your opponents will find it much, much harder to force you out of position, since he hadn't been doing so before - you had been doing that all by yourself!