Thinking about a girl alot kills you're chances with her. Thinking about her before approaching, or even before you two meet up is bad. We all know the tragedies of AA, oneitis, and living in your head. But why? Why must we focus on more than one girl? Because when you think about one girl or even the situation you feed your ego. Your ego starts to construct the "right" way to approach this girl, the "right" responses. Soon after all this you are living inside your head, planing it all out, telling yourself what to think, what to feel, how to act and react. You're afraid to live outside of your preconceived reality because you fear that it will not line up with the identity your ego has created. Essentially you're putting on a mask, you're feeding your ego and refusing to place your trust in who you are. Thinking everything through is NOT confident. Confidence is placing your trust in yourself, that you are good enough for her, for that group, for this party, etc. Last night i went to a party because i wanted to hook up with a girl that i knew would be there. I thought about her alot and she was interested in me. But i screwed it up, I tried to plan everything out, what i'd say, what i'd do. Because of this i was living in my head and afraid to approach not only that girl but other cute girls i saw. I acted out everything in my head, what the cool me would say. The cool me was my ego, it was a voice of who i believed i had to be in order to be attractive. Because of this i just imagined how the night was going to go instead of just going for it. I was afraid to go outside of my comfort zone, I was second guessing myself, feeling out of place, and just anti social. My ego made excuses and i believed them. Because of this i blew an opportunity with a pretty cute girl, but that doesn't matter since i learned from it, besides there's an abundance of beautiful women in the world.

TL;DR Just read it, i know its long but i just restate myself several times to make sure the point is driven home.

edit: remember even if you don't get the girl still have an awesome night. Just because you're living in you're head doesn't mean you should allow this girl's reaction to dictate the rest of your night. Also watch this video on oneitis since that's what a lot of you, i myself included, are struggling with, best of luck! http://www.youtube.com/watch?v=GdnYedTpToA

edit 2: how to let go of your ego and be vulnerable. http://www.youtube.com/watch?v=iCvmsMzlF7o