I have had this occur to me many times earlier before I knew about PUA. I find I am in mid game with a girl, suddenly 1 day she shows big interest in sex with me, its like a window of opportunity, though the girl is interested but since I didnt have much of a game, she showed this opportunity and presumably shut it for some time, but I am not able to identify it or not able to act on time, later on when the moment is gone I get it what was that.

I have had this happened to me currently as well - I am learning the game currently so not that great at the moment. So with such girls when I talk about it next day, they are in different moods or so they act. How should I tackle them knowing they are interested just that they are acting on their own terms
My current game skill is to get a #close but I am learning the game after that.

You are right about the window of opportunity.

Women are not like men with attraction, there attraction is less consistent and may vary from time to time, they will provide attractive men with an opportunity to approach and seduce them but if he blows that opportunity then chances are he will not get another.

Be careful with 'The Game' it is a good book for starters but there is a lot of bullshit in there as well.

Just some tips.
-Do not peacock, dress well instead, look to celebrities for your fashion sense not magicians.
-Do not learn magic tricks, unless you are a professional magician this will just make you look like a geek.
-Do not use lines or routines, this is a trap. You will not learn to develop your own charisma and communication skills, you will just be a routine robot.

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"Stay hungry, stay healthy, be a gentleman, believe strongly in yourself and go beyond limitations.” - Arnold Schwarzenegger