"If you like him, don't sleep with him right away!" That's the one piece of relationship advice that most people can agree on. But is it valid? Does sleeping with a guy right away actually mess up your chances of having a relationship with him? The truth is: it really depends on the guy. When researching my book Are All Guys Assholes? I traveled around the country speaking to over 1,000 guys about sex, love, and dating. One question I asked them was: If you met a girl and slept with her that night, what are the chances that it will turn into a serious relationship? Here is what they said:

• 9% Impossible
• 28% Unlikely
• 21% Possible, but I'd be hesitant
• 35% When I sleep with her is irrelevant
• 7% None of these answers describe my feelings

One thing I've learned after talking with so many guys is that (on the whole) they're screwed up when it comes to sex. They're told they're supposed to want it all the time. They're told that if a girl wants to have sex and they don't they're a wimp. They're also told that if they're horny, instead of exercising restraint, they should give into their desires. All of this means that many guys will have one night stands and casual sex even if they don't actually enjoy it. Even if it will make them feel grossed out the next day, some will do it anyway. And then some, instead of saying, "that was gross," or "I'm gross for doing that" will attribute that gross feeling to the girl: "She's gross for sleeping with me." (Hence, the 9% who wouldn't have a relationship with a girl they slept with on the first night).

I don't believe in hard and fast rules, or one-sized fits all advice—every situation is different. I don't agree with the advice "if you like a guy don't sleep with him right away." But what I will say is this: there is never any harm in waiting. And that's true for guys you really like as well as guys who turn out to be total tools. Why not give yourself an extra day or two to think through whether or not you want to sleep with them? Make both you an him take a time out to asses what you're doing, so you can come back for pre-meditated sex, not just a spur of the moment sex.

Sex is an intimate act, and jumping into it right away can stir the pot before you have a stable enough foundation to withstand the stirring. What if he performs awfully? And is so embarrassed that he decides to cut his loses and not call you again? Then you freak out that he hasn't called because he was never actually interested and just wanted to get laid. Why deal with that? Demystifying The Female Libido

When you first meet a guy, you don't know him that well, you don't know if he's part of the 9% who's going to discount you for sleeping with him. Or more likely he's part of the 49% on top of that who would be at least hesitant to get involved with you if you did. If you're with a guy you really like, you've just met him, and you're contemplating whether or not to have sex, ask yourself this question: "Is there really enough benefit to sleeping with him now? Or can I go home, reassess, and pick this back up in a few days?" While I'm not one to speak in absolutes, I'd be willing to bet that the opportunity to sleep with him is not a "now or never" type deal.

The research described in this article is from Amber Madison's book, Are All Guys Assholes? Learn more about her and the book at . Want to know if the guy you're dating is an A-Hole? Download the app created from her research, A-Hole Tester.

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