Imagine this: you are two ambitious members of a couple with demanding, interesting jobs and you face a major life decision together. Maybe you're expecting a child, blending your families, or making a move to establish a household together for the first time. How do you go about discussing how you will divide responsibilities and make sacrifices to make the new arrangement work? 

If you're like most two-career couples without unlimited bank accounts, you start with the practicalities. How much does childcare cost? Where is housing more affordable? Who has the higher salary, more scope for career growth, or opportunity for a flexible schedule

You look at these nuts and bolts questions and then you sit down, hammer out a plan, and hope for the best. It sounds sensible, and talking about logistics is certainly an essential part of family life, but according to INSEAD professor Jennifer Petriglieri, this is exactly the wrong way to go about making major joint decisions. 

Life isn't all about practicalities. 

Petriglieri speaks from experience. Half of a dual-career partnership herself, she also studied more than 100 ambitious couples in-depth for six years for her upcoming book, Couples That Work. The results of all that research are on display in an in-depth Harvard Business Review article this month, which is well worth a read in full if you and your partner are doing a two-career juggling act. But one lesson really stands out -- many of us are terrible at negotiating big turning points with our partners. 

Our intentions are usually good. We want to keep everyone thriving and happy. And our instincts are understandable. The daycare bill and mortgage must get paid. But Petriglieri's research revealed that while practicalities are important, they're far from everything. Too many couples ignore the less concrete issues at stake in these discussions. 

"Many couples focus on economic gain as they decide where to live, whose career to prioritize, and who will do the majority of the child care. But as sensible (and sometimes unavoidable) as this is, it often means that their decisions end up at odds with their other values and desires," she cautions. 

"Few people live for financial gain alone," she points out. "In their careers they are also motivated by continual learning and being given greater responsibilities. Outside work, they want to spend time with their children and pursue personal interests. Couples may be attracted to a location because of proximity to extended family, the quality of life it affords, or their ability to build a strong community."

In short, big decisions aren't just about practicalities. They're also about values, fears, and self-image.The most successful two-career couples talk about these things explicitly. 

"Negotiating and finding common ground in these areas helps them navigate difficult decisions because they can agree on criteria in advance. Doing this together is important; couples that make this arrangement work, I found, make choices openly and jointly, rather than implicitly and for each other," Petriglieri continues. 

Talk about values, not just money.  

There are multiple ways to make it work as a two-career couple. One partner can take the lead role professionally, the other at home. They might take turns, one focusing on career for a time while the other one steps back, then switching. Or they could both go at their careers with all guns blazing and equally share the burden at home. These can all be good options. The key is finding the one that works for you not just logistically, but psychologically as well.  

One partner taking on the role of breadwinner might make the most sense from the perspective of cold, hard math, but if the partner taking a step back has his or her sense of self tied up in work, bitterness can bubble up. Similarly, relocating to be closer to family might seem sensible, but how will you feel if your career possibilities are curtailed because you're far from the action? 

Weighing these tradeoffs successfully means braving vulnerable, messy conversations about feelings. That scares plenty of people, but the alternative, Petriglieri found, is generally simmering resentments and eventual trouble between the couple. So next time you and your partner are at a crossroads, remember this HBR article and put away the bank statements for awhile to focus on values, identity, and emotions instead.