When people get married, the vows usually include something to the effect of "for as long as you both shall live." The possibility of divorce notwithstanding, the goal, at least, is that your marriage should be permanent. Often, however, it's not -- not necessarily because couples may split but because any long-term marriage is likely to go through a series of significant transitions that change it into a whole different relationship over time.

In this podcast, Motley Fool Answers co-hosts Robert Brokamp and Alison Southwick talk with Jennifer Petriglieri, an associate professor of organizational development at the international business school INSEAD. Author of the book Couples That Work, she joins them to talk about those personal and professional transitions and offers up some tools that can help us get through them.

In this segment, she delves into the third common transition, which takes place in our 50s: your sense of identity gets lost, you realize you're running out of time, and there are a lot of issues that you and your spouse have been sweeping under the rug for years that you really need to look at head on.

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This video was recorded on Oct. 15, 2019.

Alison Southwick: Let's move on to the third transition. In the two previous phases -- and you've touched on this a bit -- they seem very much influenced by the expectations that we put on ourselves and that the world puts on us. You need to be super successful in your career. You need to be a perfect parent. But as you reach your 50s and you peak in your career, and the kids move on, you lose a sense of identity and you realize you're running out of time. This is obviously a frightening period, but it also sounds really exciting and a great opportunity to do crazy, new things together.

Jennifer Petriglieri: It is. And you know the generation now and our generation are enjoying opportunities that no generation has enjoyed before for two reasons. One is our lives are getting longer -- which means our careers are getting longer -- and it means that period in between us having more freedom -- maybe the mortgage is paid off, the kids have left home, we don't have college fees -- and retirement is actually much longer than it has been in the past.

And at the same time, the structure of careers is changing. We know there are many more options for flexibility, whether it's freelancing work. The gig economy. Whether it's a portfolio career. Whether it's trying entrepreneurship. There's all sorts of options that our parents and our grandparents just never had.

And so what I saw at this phase was couples went in one of two starkly different directions. Either they got stuck with the loss -- I'm no longer the rising star in the organization. I remember one guy said to me, "The thing which was a real wake up was I went for a promotion and realized I was up against my protégé, who was 10 years younger than me." A huge wake-up call.

Sometimes people get stuck with that sense of loss and also often lost in the relationship. They may have been sweeping those resentments under the carpet for years and suddenly it's just the two of them left in the house with "oh, we've got to face this", and that's pretty tough.

There were also couples who felt that sense of loss, but also saw these opportunities and really did some quite creative things. Many of the couples actually started doing some things together. Now it wasn't that they all formed companies and worked together all the time, but they often did little side projects together that sometimes took them back to their youth when they got together. There were some lovely stories of couples really having this huge reinvention that, quite frankly, previous generations have just not been able to do. I think there is excitement about this phase, even though there were some though issues to wrestle with our couples.

Southwick: The schadenfreude-prone part of me really enjoyed in your book the stories and anecdotes about couples who, from the outside, seemed to have it all, but then after you talked to them and put it in your book, I got to see they were falling apart a little. Can you talk a little bit more about the "myth of the power couple"? It seems like at this point in your life -- in your 50s -- you're like, "I don't need this anymore."

Petriglieri: I think the term "power couple," is just awful, because it gives this ideal state as if these couples have everything, which no couple has. I mean, this is ridiculous. There are couples that work, though, and I think the question is what these couples at work have that the couples that don't work don't have? A lot of this comes down to whether we can maintain a balance of power in the relationship.

Often what happens over time is that power balance shifts to one person, and when I talk about power in a couple, I mean, "Do I have the opportunity to go for the things I really want to do." Now this isn't about necessarily succeeding them, but it's like, "Does the couple support me in reaching those desires?"

Let me give you an example and, of course, this is not necessarily linked to how much I earn or how much of a powerful or prestigious job I have. There's one couple I followed and she was a CEO of a midsized company. She was sometimes listed in these power women things.

But in the couple she really didn't have power at all and the way she talked about her career was, "I know I've reached an objectively successful place, but this is not where I wanted to be. There were other avenues I wanted to take, but everyday I was running on this treadmill, essentially to keep the family going and so my husband could pursue his career dreams."

And I thought that was really interesting, because then I said, "How did you get there?" Because now she's at this stage of transition, and her husband can see it, as well. But, of course, it took two to tango and, of course, it starts with one small thing. Let's sweep it under the carpet. Let's not worry about that. And suddenly in a couple a pattern develops that one is the giver and the other is the taker. And very often it's such a slow dynamic, a bit like the boiling frog, that we don't realize until five or 10 years later when there's a real sense of power imbalance which, of course, brings the resentment and the guilt into a couple.

And I think it's very easy from the outside to look at those couples and think, "Oh, it's his or her fault they've been taking." It's never like that. It's always this slow dynamic. This slow burn. And couples get into that situation because they've not been talking about this stuff. Because they have been sweeping it under the carpet.

Robert Brokamp: Our listeners can clearly figure out that you're British.

Petriglieri: Yes.

Brokamp: Your husband's Italian.

Petriglieri: Yes.

Brokamp: You live in France.

Petriglieri: Yes.

Brokamp: But all our American listeners can tie into what you're saying because really this is international, or at least in the Western-developed world.

Petriglieri: And even not in the Western-developed world. My sample for the research was global. There were a lot of American couples, but also European, Asian, Middle Eastern, and African. And I think one of the things that was most surprising in the research was how these dynamics really played out across the globe. The issues of power, who gets what they want, how do we struggle through figuring out what we want, how do we face these identity questions are pretty universal.

Of course, there are some cultural dynamics and these tend to pop up around children. Who takes care of the children? In many cultures the grandparents step in a lot more than they perhaps would in the U.S. and where I'm from in the U.K. Apart from that, it's surprising how common the dynamics are across the world.

Southwick: It is kind of crazy how within essentially a generation women went from being the ones who stayed home and raised the kids to being the ones who also go to work.

Petriglieri: Yes and no. It's funny. We think about traditional structure as the breadwinner/ homemaker, but it's not the traditional structure at all. It's a blip in the long course of human history. So until the Industrial Revolution, the idea that a woman would stay home and take care of the family was laughable.

All members of the family contributed from as young as five years old. In the farms, etc., everyone is working. And really the Industrial Revolution changed that. So there's only a period of a little bit less than 100 years where that model existed. Now we're back to, in fact, what is the norm throughout human history.

It's interesting. When you look at tribal societies -- and there's research that's been done on tribal societies, the hunter/ gatherer societies -- if we think of work in terms of how many calories we gather a day, women actually contribute a little bit more work. It's about 60/40 in terms of that.

So the traditional model has always been working couples. We've just had a blip in that period from the Industrial Revolution through to really the Second World War. The Second World War was the start of the shift back, because a lot of the men were fighting, so the women took up those roles. And it's really that small period where we have that model, which we now think of as the traditional model, which actually isn't the traditional model at all. But yes, we're really going back to where we have been for most of the existence of humans on Earth.

Southwick: Jennifer, thank you so much for joining us! We covered all the transitions in your book and these different phases. It's a very well-organized book.

Petriglieri: Thank you!

Southwick: So for our listeners out there, there's tons of tips, tools, and advice for having these conversations and navigating all of these transitions. Again, the book is Couples That Work by Jennifer Petriglieri. Did I nail it?

Petriglieri: You nailed it!