Why do they lose interest after they've slept with you?
And can you get that interest back even after you've slept with them?
Most Helpful Guy
Girls and guys both want relationships at about the same rate - out of 100 single people of the same age, both guys and girls would probably, on average, be interested in a relationship with 3-6 of them. This varies by individual of course, but this is a reasonable average.
But here's where things get VERY different: women only want to have sex with roughly the same percentage of guys they'd want to date, though these two pools of people aren't exactly the same (they'd bang a super-hot or super-popular guy without a relationship, and they don't always want to bang EVERY guy they want to date).
But guys don't link sex and love the same way that girls do - they can separate the two in a way that most girls can't. And though they only want a relationship with 3-6% of the single girls they meet, they want sex from 50-60% of the girls they meet, and for those girls not on the relationship list, that sex is JUST SEX.
Which would be fine if the guys were up-front about it being just sex (and sometimes they are), but some guys will definitely mislead, or outright lie, to get sex from a girl. To be fair, many girls can be told pretty directly that, to the guy, it's just sex, and they will be in denial, or just hope he "changes his mind", but that rarely happens.
The simple solution to this is that girls (who don't want casual sex relationships) shouldn't have sex outside of relationships. While that might not work 100%, it's pretty close, because very, very few guys are willing to actually get into a relationship just to get sex - most will break it off and seek sex elsewhere once they understand that it's not going to happen without a relationship.
Of course, this means the girl has to be willing to stand her ground, even if the guy leaves. She has to be okay with him leaving if he won't commit to a relationship, because it means he was never really interested anyway. Too many girls aren't willing to let the guy go, though, and end up being used.1