When you first open a set, you haven't yet had much time to build value, and thus you are nearly indistinguishable from every other loser guy. A girl might think, Oh great, how long is this guy going to be here? Am I going to have to go dance, or go to the bathroom, or go buy a drink, so that I can get rid of this guy?

This is not a useful frame of mind for her to be in. But it is possible to inoculate her mind against such thoughts. You can create the illusion in her mind that you are fust leaving anyway. She should always have this feeling like you are about to leave.
One way of creating this impression is to use false time constraints. This technique was first popularized by Style. A few examples:

After you deliver the first few words of your opener, use a false time constraint. Then once you reach the Hook Point, try delivering another false time constraint. Why? Because the set has now decided that they want you to stay. A false time constraint at this moment will create a fear of loss. Thus begins the cycle of baiting the target to chase.