Can someone explain why I shouldnt validate her? will it lower my chances?(I know I should be having the ¨chances¨mentality, just dont know how to word it)

What happens if I validate her? ex: compliments etc? what happens if I dont?

an example: a girl directly asked to validate her, how? we were talking and I said something like: mnnn all girls are the same, very few of them are special. She replied: and I? am I special?I said no.

but what would have happend If I had said yes?