This happens to me when I get one-itus. I become demotivated to flirt with other women because there's really only one person I want.
When this is the case I simply remind myself that flirting with other girls and being casual about it all is a key part of gaming all of them, if you show that you're obsessed with a girl you're tearing apart your game anyway, flirting around helps this.
I also become randomly demotivated for no reason now and then, I've got a good wingman whom I love very dearly though, when this happens I simply turn to him and he's pretty quick to tell me to man-up. If you don't have a likeminded friend that can motivate you then it may simply be that these girls don't do it for you. BUT remember - girls know other girls, flirting with all of them is your doorway to meeting more, even if you're not interested in the ones around you right now you may find yourself SERIOUSLY interested in their girl friends. Don't waste an opportunity to network.
Man-up
