If you're exclusively a monogamous sort of guy, this article won't apply to you at all.
However, if you ever find yourself in situations where you have one or more women you see regularly for sex, yet you're still on the dating scene, looking for new girls to pair up with, you will encounter this.
It's a phenomenon we might call The Girlfriend Pickup Dip.
The Dip looks like this: once you have a woman or two to tend to your sexual needs regularly, your motivation to seek new sex partners begins to dry up.
You may still go out, but the hunger isn't there. It's harder to get higher caliber women, too, despite everything you've been told: that high caliber women like guys who aren't needy, that women want men other women want, that women can 'smell' success... despite these things, when your drive isn't there, women can sense it, and that's the biggest thing. Because high caliber women want men who value them highly, and are willing to put a minimum level of investment in to get them.
Thus, as an almost inevitable consequence, as you bring more women into your life, and 'fill your pipeline' or 'fill up your rotation', you reach a point where your motivation to keep adding new women falls, and you are less-good at getting the really top notch girls you got at your hungriest, as well as just doing the same volume of new girls in general.
This is The Dip, and if you like multiple women in your life, it can be a thorn in your side.