What’s the fine line between showing too much interest (being needy) and not caring enough (to the point she moves on or forgets you)?

I read about how showing too much interest is a bad idea. I also read how being needy is a bad idea.

The less fuck you give the more attractive you appear to women.

However, what’s the difference between this and not showing enough interest? If I don’t give a fuck, I won’t even approach a woman (even as a friend) and I know that men have to approach first.

I notice that I’ll approach, slack off and then the girl will forget about me or start dating someone else, after she gets fed up and loses interest in me.