You immediately think, "Oh... she's bored with me already. She doesn't think that what I'm saying is interesting, and she probably can't wait to get away from me, and talk to someone who's much cooler."

Now, she might have been thinking about her menstrual cramps, or something equally unrelated to you, but because you held the belief that women like her don't find you interesting, you see her wandering attention as proof that she's not into you.
I know this might sound strange, because most people think that you form your beliefs as a result of your experience. I'm suggesting just the opposite. Your experience goes through a filter (belief) and you sort out the elements of that experience which support that belief, and discard the rest of the experience.

You literally only remember the stuff that supports what you believe about life.
Here's another example. Let's say that you belief that all women are inherently bad drivers. Well every time a woman cuts you off on the road, your mind pays attention to that and says "See, it's really true... women DO drive like shit!".

But what happens if a man cuts you off on the road. You quickly speed up to see if it was a woman, and if it was a man... you pretty much ignore it... tossing it aside as one of those freak events that hardly ever happens.

The result is that the only times that you remember being cut off on the road is when women cut you off, and you delete all those memories of men cutting you off.
Are you starting to get the picture now? Beliefs determine your experience with women and dating... and in all areas of life as well.