Most of the things I’ve learned apply to both cohabitation and marriage, except this one: Getting married really is different than living together unmarried even for many years. It’s not just the many legal and financial benefits of marriage, though. There’s a psychological difference.

My husband and I lived together for several years before getting engaged, and dated several years before that, so it’s not like there was much to adjust to after getting married. But maybe it’s the months of preparing for a wedding (and investing thousands in it) or the knowledge of how difficult (and also expensive) divorce can be that makes the commitment more ironclad, for both you and those around you. This is it. 

As soon as the wedding vows are exchanged, you’re on a different, accelerated life path. Before, you were being nagged about when you were going to get married. Now friends and family will be asking when you’re going to have a baby (a relationship- and life-changer on its own). If you have that baby, you’ll be asked when you’re going to give the kid a brother or sister. Everyone’s in such a hurry.

Even if you’re really ready for marriage and can picture the entire rest of your lives together, it’s normal to wake up some days and think, “Holy shit, I’m married forever and ever?”

Everyone knows marriage is a big commitment, of course, but even when getting married is a natural step in your happy relationship, years later when you’re more appreciative of the decades you have ahead of yourselves, you can be floored by how extraordinary it is to commit the remainder of your life to one person.

You know the saying “We’re not losing a daughter, we’re gaining a son-in-law”? Well, it works in the reverse, too: You’re inheriting the obligations, stresses, and, yes, benefits, of a whole new family. You might get along superbly with your significant other’s family now, but once you’re married, they could transform into the in-laws from hell, because now you’re cemented to your partner and they claim you as one of their own.

I’m the quiet sort of person who needs her space, but my husband’s family is full of extroverts who don’t really understand that perspective. That’s caused a lot more grief over the years than it should have (I wish we had this article back then), but I’m lucky that my husband understands me and mediates when necessary.

Others aren’t so lucky. I’ve seen couples on the brink of divorce over in-law issues rather than problems specifically between the couples themselves, so my advice would be for both sides to imagine each other’s family at their worst and how you two might handle any issues before they got bigger than the both of you. And, to be fair, know that bonding with your partner’s family at a deeper level and becoming the family member they always wanted is another surprising perk of marriage.

There’s a scene in This Is 40 where Paul Rudd’s character forces his onscreen wife, Leslie Mann, to inspect his naked bottom for hemorrhoids. It might not be as extreme as that for all couples, but after being married for some time, the raw and crude things are no longer, well, raw or crude. In fact, they’re like curiosities and, sometimes, obligations.

You might ask or be asked to evaluate nose hair or pull off a blackened fingernail—things you would never do or ask while dating—because now you two are one and almost nothing is embarrassing anymore. It’s nice to always have someone there to tell you if you have broccoli between your teeth and not feel judged by it.

I used to think that the best test of whether you could live with someone else forever is to ask yourself if you could put up with their biggest flaw—or the worst version of this person—for the rest of your life. I still think that’s a good exercise, since people become more themselves as they age—their desires, strengths, and flaws get sharper. If your partner is somewhat of a curmudgeon now, he or she will probably only become crankier and more stubborn as the years go by. Conversely, the best things you love about a person could hold you steady through the inevitable tough times.

But now I think that it’s the little things you have to look for, because in the day-in/day-out of marriage, the little things add up. Little annoyances like a nail biting habit or leaving filled water glasses everywhere are really easy to overlook during a relationship when the bigger things—the way your partner makes you laugh or how beautiful you feel around him or her—attract your attention more. When we’re “in love” we tend not to notice the small things that could drive you crazy months later, like hanging the toilet paper the wrong way.

On the flip side, it’s also the small acts of everyday kindness, respect and love that keep a marriage going. Romantic gestures like buying flowers or a surprise date out are great, but they don’t hold a candle to mundane things like unclogging a drain or taking over child-bathing duty. Doing chores becomes sexy in a way you would never imagine.

The old adage that you can’t change someone by marrying them still holds true. You shouldn’t fall prey to “fixer-upper bias,” and you probably don’t want anyone to change you either. The truth is, though, you’re probably both going to have to change or adapt, as a choice, to keep the energy and love alive.

The two biggest things are learning how to fight more productively and how to communicate in ways that might not be natural to you but make more sense to the other person. Gary Chapman, who literally wrote the book on what people should know before they get married, says that people have different “love languages” or ways they express and receive love best.

I’m not naturally a “toucher” but am learning how significant just holding hands can be. It can take a long time to learn what your partner’s silences mean (and don’t mean), that grudges can kill a relationship, and how to adapt to the ups and downs that life is going to throw at you both.

Every couple should go through at least one really tough time together before they get married, just to see how the other person handles such things.

As it turns out, Paul Reiser’s 1995 book Couplehood explains the idea of going from a singular person to an entity pretty well:

The problem is, when two people live together, there is no more Business of Your Own. Your Own Business is closed. You’ve merged and gone public. You have to run everything by the partners. And if there are too many conflicts of interest, the business may go under, freeing the partners to once again open up smaller concerns by themselves.

Like all businesses, couples engage in endless meetings to discuss areas of management concern and division of labor.

“You know, we really should call the post office and tell them to hold our mail while we’re away.”

“We? You mean me, don’t you?”

“No, I mean we. I didn’t say ‘you.’ I said ‘we.’ You or me.”

“Oh really? Are you ever going to call the post office?”

A moment to think. “No.”

“Then you mean ‘me,’ don’t you?”

“Yeah.”

Being part of a permanent team has its benefits. You come to rely on the other person to remember and take care of certain information (Psychologists call this transactive memory). I don’t have to worry about making plans with our friends or not getting lost when driving, and he doesn’t have to worry about the bills or after-school activities. (Also, I wish I had known at the start that there were some things he’ll willingly do that I just assumed he hated, because I hate them: things like grocery shopping and getting rid of telemarketers. I would’ve had him do those things sooner.)

On the other hand, now you have to put the marriage above everything else, and might even forget what you were like when you were single and “free.” It’s not a bad thing, necessarily. It’s just a lot of responsibility, being responsible to someone else.

You might think once you’ve finally settled down you can relax and live happily ever after, but nothing can be farther from the truth. The years jumble together, and if you’re not careful you’ll easily take the marriage for granted.

I didn’t know it over the years, but I think the thing that’s made the most difference for my marriage is our regular vacations and other traditions—things that force us to take stock again in our relationship and reconnect on a deep level. Just “being in love” isn’t enough to make a marriage work.

Even after decades of living together, you’ll be learning things about your partner, bit by bit, that might surprise you—or they’ll suddenly change or have different priorities and needs (“Really, you want to become a scuba diver now?” and “How come you never told me you don’t like olives?”). It’s like a dance, and you both have to keep up with each other. But what a beautiful dance it can be.

This story was originally published in October 2013 and was updated on May 25, 2021 in slideshow format and to meet Lifehacker style guidelines.