What happens between flirt and diss?

What happens when a guy flirts with a girl, things are going great everything, and the very next day acts distant and almost annoyed with her? What happened in between there? Please no attitude in your answers, I want a real answer not one of those "you're an idiot because obviously that could never happen" answers. What could have happened in a guy's brain that would cause him to flirt with a girl one day and 18 hours later act distant?
What happens between flirt and diss?
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