I have a verbal hangover from something I said (okay, yelled) during a fight with my husband last night. Something I swore I would never tell him. I know what you’re thinking — that married couples should have no secrets from each other. But I’m here to tell you that’s bull. There are certain things you should never tell your husband — no matter what. When it comes to preserving marital bliss, Grandma’s old adage still holds true: What he doesn’t know can’t hurt him. So after years of watching my friends step right in a big pile of it, and though I’m practically blinded by this big-mouth hangover, I’ve made a list of things you should never, under any circumstance, tell your husband.

1. Never admit that you hate his mother…even if he bad-mouths her first (the Silence Is Golden rule)

It can be tempting to add your two cents as your husband is telling you yet another story about his controlling, manipulative, buttinsky mother. Tempting to say, “You think that’s bad? The other day she told me all of our son’s good qualities come from her! She’s just a delusional, dried-up old cow who wishes she could be married to you and who resents the hell out of me just because you love me!” Take a deep breath and hold your tongue. Remember, he can say whatever he wants, because she’s his mommy. If you agree too adamantly, bad things will happen to your relationship, not the least of which is that your husband will never let you forget your slipup and will preface everything he says about her with, “I know you hate her, but–” To be safe, apply this rule to all blood relations, particularly stepkids. Save your opinions about his family for your girlfriends or your shrink and you’ll live a much happier life — trust me.

1. Never admit that you hate his mother…even if he bad-mouths her first (the Silence Is Golden rule)

It can be tempting to add your two cents as your husband is telling you yet another story about his controlling, manipulative, buttinsky mother. Tempting to say, “You think that’s bad? The other day she told me all of our son’s good qualities come from her! She’s just a delusional, dried-up old cow who wishes she could be married to you and who resents the hell out of me just because you love me!” Take a deep breath and hold your tongue. Remember, he can say whatever he wants, because she’s his mommy. If you agree too adamantly, bad things will happen to your relationship, not the least of which is that your husband will never let you forget your slipup and will preface everything he says about her with, “I know you hate her, but–” To be safe, apply this rule to all blood relations, particularly stepkids. Save your opinions about his family for your girlfriends or your shrink and you’ll live a much happier life — trust me.

2. Never tell him that his best friend made a pass at you…(the No Harm, No Foul rule)

“An old friendship lost over nonsense,” laments Wendy, who wishes she’d kept it to herself. “I wish I’d given Sean the benefit of the doubt at least one time. If I had, my husband would still have someone to play ball with on Sundays.” Obviously, if your husband’s buddy is a repeat offender, you’ll have to break this rule, but for now be flattered and be quiet.

3. Never confess to past infidelities…(the Don’t Tell, Don’t Tell rule)

Now, girls, I’d hope this goes without saying, but I’ll mention it anyway. I don’t care if you were 20 and drunk at the time; never admit that you cheated while in a committed relationship. On the subject of fidelity, you are above reproach. And not being a cheater yourself, you have zero tolerance for cheaters. (This is a little difficult for me because my husband and I began dating behind my then-serious boyfriend’s back. Nevertheless, I make sure to occasionally remind him that if he even had a one-night stand, I would leave him and take the children to Tangier. The threat seems to be working.) But in all seriousness, you have to ask yourself how the relationship could possibly benefit from your true confessions, and I think you’ll see the answer is not at all. Doubt can do serious damage.

3. Never confess to past infidelities…(the Don’t Tell, Don’t Tell rule)

Now, girls, I’d hope this goes without saying, but I’ll mention it anyway. I don’t care if you were 20 and drunk at the time; never admit that you cheated while in a committed relationship. On the subject of fidelity, you are above reproach. And not being a cheater yourself, you have zero tolerance for cheaters. (This is a little difficult for me because my husband and I began dating behind my then-serious boyfriend’s back. Nevertheless, I make sure to occasionally remind him that if he even had a one-night stand, I would leave him and take the children to Tangier. The threat seems to be working.) But in all seriousness, you have to ask yourself how the relationship could possibly benefit from your true confessions, and I think you’ll see the answer is not at all. Doubt can do serious damage.

4. Don’t tell him that one of your girlfriends is cheating on her husband…(the Keep Your Big Fat Mouth Shut rule)

Just keeping your own past slipups under wraps is not enough. In general, you must act as though infidelity is equal to murder. You know it exists, you’ve read about it in the papers, but you certainly don’t know anyone who has actually committed it. (This won’t always be easy. Last year a friend of mine was having a full-blown affair with a guy whose kid went to our daughter’s school. Keeping this from my husband — who would have eaten it with a spoon — was harder than childbirth.)

5. Don’t say he’s not as hard as he used to be…(the It’s Your Memory That’s Getting Soft rule)

6. Don’t make him feel impotent about work…(the I Believe in You No Matter What rule)

This is the rule I broke last night. Usually when my husband comes home from work frustrated or angry about his day, I encourage him to tell me what’s on his mind. I listen intently, try to offer advice, and always make it clear that I’m on his (read: our) side. But truth be told, I think he and his boss have a serious communication problem. Yeah, his boss may be a jerk, but he’s not a mind reader.

When my husband was passed over for a promotion recently, I endured his victim routine for several days. Then, last night, I let loose. “You expect people to know what you want when you don’t even know what you want,” I yelled. “That’s what’s holding you back at work! Forget the promotion — you’re lucky you haven’t been fired!” The look on his face told me I’d hit way below the belt, and suddenly I could see the feeling of betrayal setting in. “I thought you believed in me,” he said, looking so hurt I thought I might die. “I do,” I pleaded over and over again. But the damage was done.

This morning on the phone, my sister made me feel even worse. “Why are you being his career counselor when he needs you to be his wife?” she asked, a little too aptly, I thought. And when I repeated the exchange to my mother, who is long divorced from my father, she added, “That’s a lesson I learned too late. Don’t mix your marital problems with his business problems or you’ll end up with a husband who feels like a loser at the office and at home!”

7. Don’t tell him you want a divorce unless you really do…(the Don’t Give Him Any Big Ideas rule)

My good friend Clare used to threaten her husband with divorce all the time, yet the day he took her up on it she was so shattered she had to be hospitalized. A year later her ex-husband told me, “Every time we had a fight, Clare would say maybe we should split up. Honestly, I couldn’t live with that hanging over my head anymore. I believed she had one foot out the door.” When I told Clare what her ex had said, she sighed, “Oh please, I would never have left him. He was the love of my life.”

I know we’ve all been tempted to scream “I want a divorce!” I definitely had to restrain myself during the no-sleep baby years. I remember one horrible fight Patrick and I had over whether to use the Ferber method to sleep-train our daughter. In retrospect, the argument was about supporting each other even when we disagree. But in that moment — we were locked in our bathroom so our daughter wouldn’t hear (though, trust me, people across the river could hear) — I screamed, “Get out!” The words froze between us. My husband looked at me like I was crazy. “I’m not going anywhere!” he said, and I was so relieved I burst into tears and have never threatened to throw him out again.

Once you introduce the idea of abandonment into your relationship, distrust can grow. You can’t unring that bell, so don’t ring it unless you’re sure the whole damn town is on fire.

8. Never tell him that it does bother you that you make more money than he does…(the Being Married to You Is a Full-Time Job rule)

Since three out of four of my best friends make more money than their husbands do, I’m thinking this situation is a lot more common than anyone is admitting. For years my husband made more than I did, and he couldn’t have been more generous. But as the financial balance shifted, I can’t confess to the same generosity. What was always “our” money suddenly felt a little more like “my” money, and I had to bite my tongue when I felt like saying, “Do you really need a new car?” or worse, “– a new suit?” When anybody asks me if it feels strange to be the primary wage earner, I’m quick to say no. But when I’m with my close friends, we confess that it does.

“Just last week, on our tenth anniversary, Howard gave me a beautiful pair of pearl earrings,” confided my friend Susie, a lawyer whose husband is a writer. “All I could think was, I wonder how much these cost me. It was terrible!” But as she went on to describe their evening together — how Howard had planned every detail, written her a beautiful card, bought a bottle of her favorite wine — we all realized how lucky she is to have a husband whose mind isn’t so caught up in his business that he forgets about his wife. Susie said she learned long ago that if she busts Howard’s balls about not making enough money, she has to get into bed at night with a man who doesn’t make enough money — and has busted balls!

9. Don’t confess to your crushes…(the Do Unto Others as You’d Have Them Do Unto You rule)

I am the worst when it comes to schoolgirl crushes. Every few years I meet someone who I suspect could have been the love of my life. My most recent crush (I got over him real fast when I saw him pick his ear and then smell his finger!), a hippie artist, connected with the parallel me who could have been a painter (as opposed to the real-life mommy me, who can’t even paint a toenail). When I talked with him, my mind felt alive with ideas I hadn’t had since college. As someone who has been married for more than a decade, I welcome these pseudo-romantic diversions, though I never act on them. I just flirt a little, irritate my friends with boring stories, and entertain a new series of fantasies for a while. But I never tell my husband who the object of my secret affection is for one simple reason: I would never want to know who he has a crush on. It would make me insane. A harmless crush is something no flesh-and-blood person can compete with, so I keep mine to myself. Hey, does he really need to know why you seemed sooooo into the sex the other night? And do you really need to know why he was so excited? Exactly.