Lifestyle: 7 Things you should never tell people about your relationship

It's totally natural for you to spill your guts to your girlfriends about what's going on in your relationship — hell, it's practically a right of passage at brunch or book club — but that doesn't mean you should share everything.

There are a few things that relationship experts deem worthy of staying between you and your S.O. Find out what they are, and no matter how much you want to bond with your BFFs, keep your mouth shut.

1. When you're going through a sex slump. Let's set the scene: You and your guy haven't had sex in a few months. You're not sure why, so in a fit of frustration you tell your coupled-up friend. Her response? "Oh, don't worry, we haven't either. It's been four months."

While that may give you a huge sigh of relief, Irina Firstein, a couples therapist in New York City, says it's not very helpful. "This kind of comment normalizes a problem that needs to be addressed," she explains. "Your friend is trying to help, but she's probably not because she's untrained in sex therapy and can't usually give constructive feedback."

Plus, whether she admits it or not, Firstein says it's likely she's lying. "Your sex life is actually really private, and many people tend to not be completely honest about theirs in an effort to relate to the person they're having the conversation with," she explains. In the end, her comments can make you feel worse (or better) about your problems, which is ultimately not helpful. So, if you're having problems in the bedroom, first try bringing it up with your partner. If you can't get to the root of the issue together though, consider talking with a sex therapist who can not only help you figure out why there's a lack of intimacy but also give you ideas to spice things up in the bedroom.

2. When your in-laws piss you off. It seems like everyone bitches about their mother- or sister-in-law, but Firstein says you should try to bite your tongue if you can. You never know when word is going to get back around to your husband (or if he simply overheard you in the other room), and that can make him resentful, "as typically people are defensive of their family," she explains.

And again, it's not helpful. Sure, it'll make you feel better in the moment to get a frustration off your chest, but ultimately the feedback you get from friends will be personal and likely drawn from their own experience. "That has nothing to do with you and your situation, so it's safer not to risk it," says Firstein. Instead, go get in a workoutto blow off some steam, then come back and talk to your partner, so you can work out a solution after you've had some time to cool off and can speak (and think) more clearly.

3. When your partner reveals his sexual fantasy. In season three of Friends, a whole episode is devoted to Rachel telling Phoebe about Ross's Princess Leia fantasy — and Ross being pissed about her sharing that secret. His frustration is warranted, says sex therapist Vanessa Marin. "Most of us have fantasies that we're not entirely comfortable with; it's a big deal to let down your guard and share the most intimate parts of your sexuality with another person," she says.

As his partner, Marin says you should honor that trust and keep the information private. It may be tempting to talk about if there's a big shock value to the confession, or if you don't know how to tell him you're not all that keen on making it a reality. But resist and keep that info to yourself. (After all, how would you feel if he talked about your fantasies with his buddies?) If you need to talk to someone, book a session with a sex therapist.

4. When one of you cheats. Whether it was an emotional or physical affair (yes, there's a difference and yes, they're both considered infidelity), any acts that had you or your partner straying outside your relationship need to be kept quiet, says Firstein. It's common to want to vent to someone else — say, your mom or your best friend — but Firstein says that can irreparably damage their opinion of your partner. And while that may be NBD if the two of you decide to separate, if you want to make a comeback, it'll be that much harder.

"Because others know about it, it will linger on and you'll have to deal with their feelings and judgment for however long they decide," says Firstein. Think about it: If your mom knows, then every time you have a small fight with your guy and need to vent, she'll always be able to bring it back to the affair, even if it has nothing to do with that. (Plus, just imagine the daggers of hatred shooting from her eyes at every family get-together from there on out. Awk-ward.) Instead, talk to an individual or couple's therapist about the affair whenever you need to — they create a safe space for you to get your emotions out without a side of judgment.

5. When one (or both) of you is going through something private. It sounds like a given, but Firstein says it's worth repeating: If your partner confides in you about a privatefamily matter (his sibling has a serious health condition, for example) or a less-than-ideal situation he's in (like the loss of a job), keep your mouth shut. When he opens up to you like that, it's proof that he trusts you and your ability to handle the situation in a respectful manner, she says.

Don't break that trust by opening up to someone else — even if it's simply because you're looking for advice on how to console him. Instead, "it's best to just listen and be there," says Firstein. "It's a touchy issue, but the best thing you can do is let him talk, and be caring and empathetic."

6. When he makes a money mistake. Making a mistake is embarrassing enough, but when it's about money it tends to be even more personal, as finances can be one of the biggest causes of divorce, says Firstein. So don't cut him down by talking about it in public. Whether he made a bad play in the stock market or exercised poor judgment in his spending habits that month, it's a personal transgression that's just that — personal.

Talking about it to your friends makes him look bad, which inevitably changes their opinion of him, says Firstein. If you need advice on how to bounce back, try these money-budgeting tips and consider consulting a financial adviser to help you both get back on track.

7. When your partner has a smell, taste, penis size (whatever) that you didn't expect. When you first start seeing someone, it's common for both men and women to dish details to their friends about their partner's body, says Marin. After all, what woman hasn't had a rowdy conversation with her girlfriends detailing her latest hookup? But if the guy is someone you could potentially see yourself dating long-term, you may want to pause, she says. "Your friends are going to eventually meet him, and your partner would probably be horrified he ever found out you shared this really personal information," says Marin.

Now, that's not to say you can't say anything — he'd probably be stoked if you were vague and simply bragged on his skills a bit — but if it's something that could potentially embarrass him or that he's already insecure about (like having a smaller penis, for example), keep it to yourself.