1. Someone else’s significant other.
You would think this goes without saying, but it’s surprising just how many people can’t seem to get this when in the heat of the moment and presented with a sexy little piece who just happens to be attached. The desire can be overwhelming, and you can even manage to convince yourself that their current SO isn’t good for them or isn’t what they really need but SPOILER ALERT: That isn’t your choice to make. If they are really unhappy in their relationship, it’s up to them to do the decent thing and get themselves out of it before they go frolicking through the genitalia forest with impunity. Nothing good comes from being the Other Person, and it makes you kind of a terrible person (no matter how good the sex is.)
2. Your roommate.
Do not, I repeat, do not, bone the roommate. I have witnessed more than a generous handful of otherwise-copacetic living situations devolve into a cess pool of awkward half-feelings, demi-jealousy, and discreet handjobs. There is just no way to make a dignified exit when you’re stuck living with this person through, at the very lease, the end of your lease. It’s like trying to slam a revolving door — you just can’t make things as clean and final as you want them to, and you end up looking ridiculous in the process. The two possible outcomes of a roommate tryst are: you end up happily ever after, and the exchanging of co-habitating fluids never presents a problem, or one of you has to move out. There is no alternative. None.
3. The ex it’s never going to work with.
Stop doing this. Yes, it’s easy. Yes, it’s convenient. Yes, you guys know what the other one likes. Yes, there is a spicy bit of complicated feelings to make the whole thing feel passionate and fresh, when really it’s just two exes having sex in the back of a Civic parked out by the movie theater. But these are not valid reasons to keep stretching out the already-awful “let’s stop hurting each other process” and making the blurry lines between the two of you even more… moist. Best to just leave them in the past where they belong, at least until you can think of more constructive things to do as “friends” than illicit fornicating.
4. Someone who isn’t that into you.
Man, doesn’t it feel great when you’re with someone, and you can tell that they consider the act of sleeping with you to be a huge favor to you? You know, when you’re really, really into them and all they seem to be is vaguely bothered by your desire for their affection in return? It’s just awesome when you can feel them trying to extricate themselves from the bed the second the actual sex is over, lest you interpret their post-coital spooning for an indication of deeper feelings. It’s maybe the best feeling ever, honestly.
5. Someone you’re not that into.
Yeah, never do this to anyone else. It’s the worst.
6. The person you’re trying to break up with.
If there is something more oppressive to the human spirit than the act of sleeping with someone who you have not yet found the courage to break up with, I don’t want to be aware of it. It’s just like, how much more cruel can you be? How much more empty or deceptive of a physical act could there be? It’s basically the emotional equivalent of having sex with a corpse, only more damaging and awful. I’m shuddering just thinking about it, honestly. Let’s all collectively vow never to go there again, for the betterment of humanity.
7. Your boss.
This is a bad idea. You know it’s a bad idea, and you still kind of want to do it anyway when the opportunity presents itself because, come on, that shit is like some terrible erotic novel. You’re ready to get yourself into some 50 Shades shit and start knocking boots over on the Xerox in accounts receivable. But it’s just a bad idea, and nothing good will come of it. Come on, you know that.
8. Your friend’s ex.
There is a code in life. I don’t adhere to all of the individual rules personally, but I know there are certain ones that should not be transgressed — and sleeping with the ex of a friend is amongst the crimes that deserve the social version of the death penalty. If the friend is not 100 percent over the ex, if you have not spoken with your friend about this openly and obtained his or her approval beforehand, and if you don’t handle everything with the utmost respect, you are basically a real-life Disney villain. And even then, tread with caution.