At the point where Keltham noticed that he'd been surrounded by pretty girls his own age, he'd been about to... ask around for library-help, in case he was looking in the wrong place to find subject-encyclopedias.
Keltham observes of himself that he is, in fact, scared, even armed with his new Plan.
The stereotypically Wise question to ask when you're scared is, "Suppose you go on avoiding this forever, how well will that work out for you?"
And Keltham knows well that he does not, in fact, wish to avoid talking to amorous female hordes forever. Every man must, at some point, talk to the amorous female hordes bent on mating with him, and pretend not to notice. This is wisdom.