Supposing for the sake of inquiry that Sally is ambivalent about or indifferent to the presence or absence of sex in her relationships (but suitably enthusiastic once it's been introduced), and just wants to minimize the probability that she'll be dumped, what should she do? It's hardly unheard of for women to be dumped for not putting out, even if the model you offer of Bob's subsequent loss of interest is accurate.
Before even getting into any tactical considerations, Sally should try to make a cool-headed strategic judgment of whether there is in fact a significant chance of not getting dumped. For women, it's easy to get delusional in this regard because as a general rule, the attractiveness of men a woman can get for casual sex and non-serious relationships is significantly higher than the attractiveness of those she can get to really commit. From what I've observed, women get dumped and heartbroken much more often because of such strategic blindness leading to relationships where they are doomed from day one than because of tactical missteps.
Related to: Luminosity Sequence, Unknown Knowns,
Let me introduce you to a hypothetical high school student, Sally. She’s smart and pretty and outgoing, and so are her friends. She considers herself a modern woman, sexually liberated, and this is in line with the lifestyle her friends practice. They think sex is normal and healthy and fun. Sally isn’t just pretending in order to fit in; these really are her friends, this really is her milieu, and according to health class, sex between consenting adults is nothing to be ashamed of. Sally isn't a rigorous rationalist, although she likes to think of herself as rational, and she's no more self-aware than the average high school girl.
Now Sally meets a boy, Bob, and she things he’s cute, and he thinks she’s cute too. Bob is part of her crowd. Her friends like him; he respects women and treats Sally well and, like any healthy teenage boy, fairly horny. According to her belief system, that shouldn’t set off any alarm bells. She’s been warned about abusive relationships, but Bob is a nice guy. So when they go upstairs together at her friend’s party, she has every reason to be excited and a little nervous, but not uncomfortable. The idea that Mom wouldn’t approve is so obviously irrelevant that she ignores it completely.
...And afterwards, she feels guilty and violated and horrible about herself, even though it was her decision.
I used this example because I expect it’s not unusual. On the surface, Sally’s discomfort seems to come out of nowhere, but modern North American society is chock-full of contradictory beliefs about sex. Sex is normal and healthy. Sex is dirty. Sex is only for when you’re married. If Sally’s mother is Christian, or even just conservative, Sally would have internalized those beliefs when she was a child. It would have been hard not to. They’re her unknown knowns, and she may not have noticed them before, because there’s a wide psychological gap between believing it’s okay for others to behave a particular way, and believing it’s okay for you. The meme ‘don’t pass judgement on other people’ is, I think, pretty widespread in North America and maybe more so in Canada, but so is holding oneself to a high standard...and those are contradictory.
I think that the nagging, seemingly irrational moment of ‘that doesn’t feel right’ is important. It potentially reveals something about the beliefs and attitudes you hold that you don’t even know about. Sally’s response to her nagging doubt could have been the following:
Hmm, that’s interesting, why does it bother me so much that Mom would disapprove? I guess when we used to go to church, they said sex was only for when you’re married. But I don’t believe anything else they said in church. ...Well, I guess I want Mom to be proud of me. I want her to praise me for doing well in school. And I think lying is wrong, so the fact that I either have to lie to her about having had sex, or face her disapproval, maybe that’s why I’m uncomfortable? But I don’t want to say no, it’ll make me look like a prude... Still, what if everyone feels this way at the start? I know Alice went to church too when she was a kid, and her mom would kill her if she knew she was sexually active, I wonder if that bothers Alice? Hmm, I think maybe it’s still the right choice to sleep with Bob, but maybe I’m taking this too lightly? Maybe this should be a big deal and I should feel anxious? After all, he might judge me anyway, he might think I’m too easy, or a slut. Maybe I can just explain to him that I want to think about this longer... After all, why should I assume something is right just because they told us in health class? That’s just like in church, it’s taking someone else’s opinion on faith. I’ve never actually thought about this, I’ve just followed other people. Who’s to say they’re right?
Whatever decision Sally makes, she probably won’t feel violated. She listened to her feelings and took them into consideration, even though they seemed irrational. As it turned out, they were a reasonable consequence of a belief-fragment that she hadn’t even known she had. So as a consequence of stopping to think, she knows herself better too. She’ll be better able to predict her behaviour in future situations. She’ll be less likely to ignore her threshold-warning discomfort and make risky choices as a result of peer pressure alone. She’ll be more likely to think.
To conclude: emotions exist. They are real. If you ignore them and plow on ahead, you won’t necessarily thank yourself afterwards. And that nagging feeling is a priceless moment to find out about your unknown knowns...which may not be rational, which may have been laid down in some previous era and never questioned since, but which part of you is going to try to uphold until you consciously deconstruct them.