1. How many people he's slept with. There's no way you're going to get a straight answer out of him. Numbers are being fudged one way (or, if he thinks it'll impress you, the other). And even if you do get a number out of him, good luck getting much more info than that. Don't even bother asking him about the best sex he's ever had (the answer is you, by the way).
2. If he's ever dumped someone... and it didn't go well. He doesn't want to tell you about the time sophomore year he dumped a girl a day after they slept together. Because he was an idiot then, and he's embarrassed about the whole thing.
3. If he's ever taken a breakup way too hard. Did you know he once spent an entire week in bed, crying, and skipping classes? No, you don't know that, and you never will.
4. The weird things he did as a kid and will take to his grave. Everyone was a stupid kid, and everyone has that one (well, probably more than one) awkward or cringy moment of poor judgement. The kind that's impossible to explain to another human being. (Did you ever eat your friend's booger? Me neither.) He's not even going to bother trying.
5. Basically all of college. You are not your best person at school. You are a drunken buffoon. It's best not to talk about college. And if you met in college, it's best not to talk about whatever happened before you met in college.
6. How he really feels about that one friend you have suspicions about. It's not like you have anything to actively worry about, but if there was ever sparks between him and an old friend, he'll downplay the hell out of it. He's not trying to hide anything from you, he just doesn't want you to worry for no reason.
7. The story behind his most awkward one-night-stand. This is the one story all his friends know and you don't. Because telling you would be weird.
8. That thing he fantasized about while masturbating once (or twice) and is a little embarrassed about. Fantasies are meant to be fantasies, and sometimes it's best not to know what's in your partner's Internet search history. Cartoons? Pee? Cartoons peeing? Someone is looking at that stuff online, and statistically speaking, they have to be someone's boyfriend? Maybe it's yours. Who knows. It's fine.
9. That he was basically broke when he met you. If he was struggling, or not doing great at his job, he sure as hell wasn't about to tell you. Men are told we're supposed to be providers, so he's not going to let slip that your last lunch date cost him a LOT.
10. If he's ever cheated on a girlfriend. He may have made a dumb mistake in the past that was out of character and he doesn't want you to think any less of him. Or he may be a piece of shit serial cheater in which case, well, he's lying to you all the time. No matter the case, if he's done it (emphasis on if), he'd probably rather not tell you.
This article originally appeared on Cosmopolitan.com. Minor edits have been made by the Cosmo.ph editors.