Last week a reader sent me a long email. He is a man in his thirties who has been dating a woman for about a year. Everyone in his life likes her. His mother likes her. His friends like her. He wrote that she is kind and funny and easy to be around, and then he asked me a hard question. He asked how to tell the difference between a woman who is nice and a woman who would be a good wife.

I am not a counselor. I am a former teacher and a stay at home mom of three kids, and I have been married long enough to know that nice is not the same thing as steady. So I did what I usually do. I asked readers of this blog to tell me the habits that worried them most, in their own marriages or in the marriages of people close to them. I read the replies at the kitchen table every night during the first week of December while I wrapped gifts and my husband put our three kids to bed.

I also watched my own week closely. Several of these habits I have caught in myself. That is the honest part of this list. These are not habits that make a woman a bad person. They are habits that make a marriage hard to keep.

She keeps a running tally of every favor

On Monday night my husband came home late and I had already done bath time for all three kids by myself. I noticed a little voice in my head start counting. I had done pickup, dinner, dishes, and baths, and my husband had done none of those things. By the time my husband walked in I had a list ready. I did not say the list out loud, but it changed how I greeted my husband at the door. I was cool and short with my husband for an hour over a tally my husband did not even know existed.

A reader named Carla M., 44, from Fort Wayne, Indiana, wrote about her brother’s marriage. She said, “My sister in law keeps a mental ledger. Every ride, every dinner, every time she watched the kids. Nothing is ever just given. It is a loan, and my brother is always behind on payments.” A marriage cannot run on a ledger. The takeaway is simple. A woman who counts every favor is building a debt, not a home.

She is sweet to your face and sharp about everyone else

On Tuesday a friend from down the street stopped by for coffee while my youngest napped. We talked about the school fundraiser and the new family on the corner. Then I caught myself saying something unkind about a mom from the school pickup line, a woman who had never done anything to me. My friend laughed, and I laughed, and then I felt a little sick about it after my friend left. The mom from pickup was not there to defend herself. That is exactly why it was easy.

A reader named Devin R., 38, from Chattanooga, Tennessee, put it plainly. He wrote, “The way a woman talks about her coworkers and her friends when they are not in the room is the way she will talk about you to her sister when you are not in the room.” Kindness that only shows up in front of the person it benefits is not kindness. It is a performance. The takeaway is this. Watch how a woman treats people who cannot do anything for her.

She hides spending and small decisions

On Wednesday I bought a winter coat for our middle one and tucked the bag in the hall closet. I had not told my husband. The coat was needed, and the price was fair, but I still hid the bag. When my husband asked about it that night I felt caught, which told me something. I was not hiding the coat. I was hiding a habit of deciding things alone and reporting them later, or never. My husband was not upset about the coat. My husband was tired of finding out about things after the fact.

A reader named Priya N., 41, from Mesa, Arizona, wrote about her best friend. She said, “My friend has a credit card her husband does not know about. She says it is no big deal because she pays it. But he does not know about the card, and that is the whole problem. The secret is the problem, not the balance.” Marriage runs on shared information. The takeaway is that a woman who hides small things is practicing for bigger ones.

She cannot say the words I was wrong

On Thursday my husband and I had a short, stupid fight about the thermostat. My husband was right. I had turned it down and forgotten, and our oldest had been cold all afternoon. Instead of saying so, I brought up a time last spring when my husband left the garage door open. I watched myself do it. My husband let it go, which is one of the kind things my husband does, but the moment stayed with me. I had traded a two second apology for a five minute detour.

A reader named Tom W., 52, from Scranton, Pennsylvania, wrote about his first marriage. He said, “In eleven years I never once heard my ex wife say she was sorry. Every argument ended with a list of my faults. I stopped bringing things up at all, and that silence is what ended us.” A woman who cannot apologize leaves her husband with one choice, to swallow everything or to leave. The takeaway is plain. Someone who cannot admit a small wrong will not be able to repair a big one.

She is kind to you and cold to your family

On Friday my mom called while I was making dinner. I was short with my mom on the phone, not rude, but clipped. Our youngest was crying and the pasta was boiling over. After I hung up, my husband said quietly that my mom had sounded lonely. My husband was right. I had treated my husband with patience all week and had given my mom the leftovers. I called my mom back after dinner. A marriage is not only two people. It is two families, and the way a woman treats her husband’s parents and siblings matters a great deal over time.

A reader named Lorraine B., 63, from Duluth, Minnesota, wrote about her son’s wife. She said, “She is lovely to my son. To me she is polite in the way you are polite to a cashier. In nine years she has never once asked me a question about my life.” The takeaway is this. A woman who cannot make room for the people her husband loves is asking him to shrink his life to fit hers.

She checks out when things get boring or hard

On Saturday nothing happened. That is the point. My husband cleaned the gutters. I folded laundry while our three kids built a fort out of couch cushions. We ate leftovers. Nobody took a picture of anything. I noticed that I felt restless around four in the afternoon, and I thought about how easy it would be to let that restlessness turn into a complaint about my husband. Marriage has long stretches of nothing. Then it has long stretches of hard. A woman who needs constant excitement or constant ease will struggle with both.

A reader named Marcus H., 46, from Spokane, Washington, wrote about his wife of many years. He said, “The best thing my wife ever did was stay interested during the boring years. Diapers, bills, my dad getting sick. She did not need every day to be a date night. She just stayed.” The takeaway is simple. A woman who leaves the room, in her head or in her heart, when a season turns dull or heavy is not ready to be married.

By Sunday night the gifts were wrapped and my husband and I were sitting on the couch with the last of the reader replies. I had found myself in four of the six habits on this list in a single ordinary week. I told my husband so. My husband laughed and said he could find himself in a few of them too, which is fair, because none of these habits belong only to women.

That is what I wrote back to the reader who sent the email. The question is not whether a woman is nice. Plenty of nice people are hard to be married to. The question is whether she can be trusted when no one is watching, whether she can apologize, whether she can stay. Which of these habits have you caught in yourself lately?