OKAY, SO FIRST things first: We’re not exactly encouraging you to lie to your girlfriend.

“A good relationship is based upon trust, honesty, and intimacy,” says Bela Gandhi, founder and head coach of Smart Dating Academy, a dating consulting firm for professionals. You know the most important things about one another, know in your gut she’s being honest with you, and you can trust her with anything.

Sometimes, though, being too honest can derail a relationship. As our lawyer friends might say: There’s a difference between honesty and disclosure.

“Holding back information is wholly appropriate depending on the context,” says Sarah Jones, founder of the premier dating-coaching company Introverted Alpha. It’s acceptable to keep a secret to yourself when you don’t feel enough trust or comfort to share, and feel it could have a negative consequence on your psyche or reputation. Likewise, you get a green light on keeping your lips sealed if the topic might disintegrate into hurtful, unhelpful detail. That’s especially the case if you’re in the infancy of a new relationship.

You’re not going to share your darkest secrets on a first date or when you’re just getting comfortable around her. But if you’ve been dating a woman anywhere from six months to six years, here’s what’s “better left unsaid”—the secrets that won’t hurt your relationship or be considered deceitful.

1. The number of people you’ve slept with

“Nothing good comes out of revealing the number—on either side—ever,” Gandhi says. A tiny, cynical, self-destructive part of her wants to know. But telling her won’t make her feel good. If the number’s high, she could feel like she doesn’t stack up to your exes—or that you’re a womanizer, even if you’re not. And if you’ve only been with a handful of women, she can feel guilty about her number, or get paranoid you’ll ditch her to have more sexual experiences. (Here’s what to tell your girlfriend if she asks how many women you’ve been with.) If she keeps dogging you about it, explain how her persistence is making you uncomfortable and the number is inconsequential in the grand scheme, because you’re with her and only her. Let the past be the past. But definitely make sure you both get tested for any STIsregardless of how many people you’ve slept with.

2. How great your ex was

“A recent client of mine told me she almost dumped her now-fiancée early on because he said his ex looked like a ‘porn star,'” Gandhi says. “She felt insecure knowing this and felt like he was judging her body against an air-brushed porn star fantasy.” Think about it if the roles were reversed: Would you want the mental image of your girlfriend’s last love interest looking something like Chris Hemsworth? Abso-fucking-lutely not.

So if she asks about your ex, absolutely do not bring up how great the sex was, how much your family loved her, or how bangin’ her bod was. Your girlfriend might wonder these things, but giving her the answer is just cruel (even if you don’t mean it).