It’s taken me 10 years and three grandchildren to finally get it. A man leaves his parents and his wife becomes his focus. Sons grow up, meet girls, get married and voila, a couple is formed.

And like it or not, when this happens the rules change.

For starters, a mother is no longer No. 1 in her son’s life. But it takes a lot of us mothers of sons a few years, maybe decades to realize this.

Mothers are the go-to person for their sons’ first 20, 30, sometimes 40 years. Then one day they aren’t. Of course we’re a little undone by the change. Some of us dig in our heels and continue to play by the old rules. Some of us insist upon standing smack in the middle of the new couple.

But we can’t forever. And we shouldn’t at all.

I’ve dug in my heels and had arguments with my daughter-in-law I wish I hadn’t. She and my son eloped. She didn’t want a wedding party a few months later. She said this straight out. “I don’t want a party.” But did I hear? Did I listen?

We had a party anyway. Invited 100 guests. Fed them dinner and drinks. Dragged her up in front of the guests and then got angry, because she wasn’t thrilled.

“She said she didn’t want a party,” my friend Anne reminded me later. She told you.

Yes, and I listened, but didn’t hear.

We do these things. I asked my mother-in-law at least a million times to “Please call before you stop by.” She never did. She’d say, “I was in the neighborhood” or “I’m not stopping to see you, I’m just saying hi to the kids” or “Just ignore me. I stopped because I made you some shortbread?” How can you get angry with someone who makes you shortbread?

But I did.

Pick your battles, my Aunt Lorraine used to tell me. So how do you avoid conflicts with your daughter-in-law? Here are some of the things you shouldn’t do and topics you should avoid:

1. Don’t talk about…The baby’s name.

My daughter-in-law refused to play the “What Are You Going to Name the Baby?” game for each of her three pregnancies.  And who can blame her. “Colum? What kind of a name is that? Brandon. Tyler. Lucy. Adam.” Everyone weighs in on a name, loving it or hating it.  She waited until each baby was born to tell us.  Megan. Luke. Euan. Embrace the name. Whatever name your son and daughter-in-law choose.

2. Don’t talk about…Where they live.

If it happens to be closer to her parents, that’s okay. If it happens to be right next door to her parents, that’s okay. If it happens to be a room in her parent’s home, that’s okay, too. You are not being replaced! My daughter and son-in-law moved in with us for a while right after their first child was born. The other grandparents, who lived 200 miles away, never acted as if we were the victors in some game of tug of war. But I felt like a victor. And I felt guilty.

A few years later when the other grandparents moved in with my son and daughter-in-law and our by then two grandkids, I felt a little replaced. But I shouldn’t have because I wasn’t. Kids love their grandparents whether they are in the tiny room down the hall or an ocean away. My son’s children, whose other grandparents live in Scotland, are constant reminders of this. They Skype. Granny Scotland sends them “parcels” all the time. And when she flies into town, it’s as if Mary Poppins has arrived.

3. Don’t talk about…Weight gain or loss.

If your daughter-in-law looks a little bigger than she used to, do not say a word. Do not give her a gym membership, a three-month pass to Weight Watchers, a subscription to Cooking Light, or a lecture about calories when she reaches for a roll. (And if you go clothes shopping together, do not tell her that something makes her look big.) People gain weight. People lose weight. Say nothing.

4. Don’t talk about…Seeing the grandkids.

Sure, you want to see them. You want to open the door and have them rush into your arms and cover you with kisses. And maybe you want to take them somewhere: to the beach, the zoo, a park, on vacation. Maybe you love playing with them. On the floor when they are little, and board games as they get bigger. But maybe not. There are two kinds of grandparents: the get-on-their-level kind and the rise-to-my-level kind. Every grandparent is as different as every grandchild. And so is every parent. Some sons and daughters-in-law love for their parents to be around and involved in their kids lives. But some need space.

Once again, the parents get to make the rules. Are you around too little or too much? Ask them. What would they like you to do? How can you help. Wouldn’t you have loved for your in-laws to ask you these things?

5. Don’t talk about…Rules for the kids.

If your daughter-in-law asks you not do something, as in,“Please don’t give the children chocolate before they go to bed,” “Please don’t bring the kids another toy,”  “Please, please, please don’t tell them stories about monsters,” listen to her. Respect her wishes just as you wanted your mother-in-law to respect yours. Grandparents are there for support, not to blaze the path with the grandkids. We had our chance with our own kids.

6. Don’t talk about…Schooling.

She likes Montessori. You prefer Waldorf. She chooses private. You believe in public. She says pre-school. You say, “Waste of money.” Don’t. We all got to raise our kids. We need to let our sons and daughters-in-law raise theirs. Where and when a child attends school is an important choice. But it’s not ours to make.

7. Don’t talk about…How she spends money.

This is a biggie. We all spend our money on things we think are important. My oldest daughter likes fancy restaurants and expensive shoes. My youngest likes concerts. I like all things Halloween. What’s a waste of money to one person is a necessity to another. So even if your daughter-in-law decides to get yet another butterfly tattooed on her arm,  say nothing. It’s her money, her life, and her arm. And really, didn’t you want to make your own decisions when you were her age? And didn’t you want to be validated?

And while you’re at it…

8. Don’t talk about…Etiquette books as gifts.

If you both read and love to talk about books themselves, fine. What I’m talking about here are books as gifts. Do not give your daughter-in-law any kind of etiquette book, a cookbook (unless she’s a good cook who loves to cook), self-help books or books about how to raise children. It’s passive-aggressive, and you know it. And, trust me, it will lead to a blow-up.

9. Don’t…Putter in the kitchen.

Do not rearrange the spice cabinet or clean out the silverware drawer or wipe down the counters no matter how much you want to. It’s criticism.

That’s all getting along is—being who you are and being accepted for it. And that’s all your daughter-in-law wants.

Beverly Beckham writes a weekly column for The Boston Globe. Bev’s new e-book The Best of Bev Beckham is currently available for free to Globe subscribers if you click here.