Why is it so hard to talk to women?

I just came back from downtown. I went to downtown hoping to get a girl. I have been reading books on how to talk to women. The tips and advices that the authors give are reasonable and they make sense. While I read the tips, I visualized myself using these tips and talking to girls. However, when I am in the real world its different. I find it so hard to approach random women because I really don't know what to say to them because they are complete strangers. I hate this; why is this so hard? Why do I have trouble speaking to women?
Why is it so hard to talk to women?
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