The day she went back to work after her first maternity leave was the day Tiffany Dufu realised that the political was personal, and that the rules of her domestic life would have to change. That morning, she’d been buoyant. Happily married, she’d landed her dream job, found a childcarer she trusted and negotiated space to express her milk while she was at the office. It wasn’t going to be easy to juggle parenting, a career and a relationship, but it was possible, and she was ready.

Six hours later, Tiffany was kneeling on the floor of the ladies’ loo, tears streaming down her face, expressing her milk into the toilet bowl. Caught up in the demands of her job, she’d completely forgotten about her breasts until they became so engorged that she couldn’t fit the suction appliance on to her nipples and she was forced to retreat to the bathroom. Suddenly, it all seemed a lot more daunting.

“I thought, if I can’t even remember to express my milk what other balls am I going to drop?” she says. “How am I going to do the shopping? How am I going to cook the meals? How am I going to do the laundry? How am I going to maintain my relationship? And how will there be any time for me to do the things I care about for myself, like reading?”

That night, after feeding her baby and putting him down for the night, Tiffany was sobbing into her pillow when she heard her husband, Kojo, arriving home from the office.

“I heard him brush against the dry cleaning I’d collected. I heard him leave his shoes in the hallway, open the fridge, get out the meal I’d prepared for him and, when he’d eaten it, I heard him drop the plate and the cutlery into the sink. And then I heard him sink into the sofa and switch on the TV.”

In that moment, says Tiffany, she realised that to juggle work and parenting she was going to have to drop a ball – and Kojo would have to pick it up.

“We’d been married for eight years, and I’d done everything my mother had done at home, and worked as well. But that wasn’t going to be possible any more – and I felt resentful, because the two of us had had a baby but it was only impacting on one career, and that was mine. We were on the same highway, but he had somehow managed to bypass the car crash that was now engulfing me.”

When Tiffany sat back to think about it, she realised that what she was doing was fulfilling the roles she was expected to fulfil. Because of the way she’d been raised – in a traditional home in Seattle, with a mother who stayed at home and a father who had a job – she had deeply ingrained ideas about what constituted being a “good” mother – not to mention a good wife, and a good worker. Now the time had come to rethink those definitions.

“It was a bitter pill to swallow, because I was a confident, empowered woman and I was having to admit that much of my behaviour was conditioned by other people. I wasn’t in the driving seat of my own life: in public I was a staunch feminist, but in private I was a Stepford wife on autopilot.”

What Tiffany decided to do, and what she recommends in her book that we all should do, was take a long, hard look at herself and work out what her priorities were.

“Lots of women say their priorities are their children, their relationship and their career – but you need to be more precise than that. I worked out that the things that really mattered to me were nurturing a healthy partnership with my husband, raising children who would be responsible global citizens, and advancing the lives of women and girls [which is what she does professionally].”

From that point, she says, her life became easier: she was able to look at her time and her tasks, and work out what mattered to her and what could go by the wayside. Her lightbulb moment was the realisation that anything she couldn’t do could be dropped – and either Kojo or someone else in their extended family or community could pick up the balls that she had let go of, or the task could be neglected.

“I had reset the rules about what being a good mother meant, so now I was more confident about what didn’t matter as well as what did.”

One of the big lessons she learned was that when you drop a ball and your partner picks it up, you have to let him pick it up his way. So when Kojo took on collecting the dry cleaning, he got it delivered. (“Why had I never realised they delivered?” asks Tiffany.) When he took on the cooking, it was chicken casserole every night for a week.

Right now, while she’s in London promoting her book, back home in New York, Kojo is in charge of getting their son and daughter, 10 and eight, to school each morning. “And what he does is wake them up, and tell them that in 45 minutes’ time they have to be at the front door having had their breakfast, and with their packed lunch in their bag,” she says. “It never occurred to me that they could sort out their own food – I was doing it for them every day.”

In a nutshell, Tiffany’s book is about why mothers should expect less of themselves, and more of their partner. She says she was suffering from what she calls “home control disease”: while she scoffed at the idea that a woman’s place was in the home, she still focused obsessively on how it was run, how it was organised, and she still believed, deep down, that only her way of doing things would work. What she now knows is that this attitude was a barrier to Kojo getting involved on his own terms – and improving not only their family life, but also their kids’ idea of who does what in the home.

Among her strategies was transferring tactics learned in the office to home life: some women are good at transferring their home organisation skills to the workplace, but less good at doing it the other way round. She created a spreadsheet and put every family task she could think of into it: beside the tasks were three columns, headed “Tiffany”, “Kojo”, and “no one”. When Kojo saw the list he came up with some things Tiffany had forgotten to include, such as booking the family’s holidays, sorting out their tech needs and watering the garden – all tasks, he pointed out, that he did. It wasn’t that Kojo was doing nothing – although he could, and now does, do more – but he prioritised tasks that Tiffany hadn’t even realised needed doing, just as she had done with tasks she usually did herself.

The spreadsheet, according to Tiffany, reduces the risk of resentment. And getting her husband to do more has given her more time to be strategic in her career: since she started dropping balls, she has been promoted at work and written her book.

“When women are freed from having two full-time jobs, they are better able to execute the strategies and adopt the mindsets necessary to transcend the glass ceiling,” she writes in her book.

Tiffany says that coming from an African-American family helped her to negotiate the pathway to fairer parenting: her parents, she said, would tell her when she was a child that because she was black, she’d have to work harder than white people – that life wasn’t fair.

“That might sound like a harsh message to give a child, but I’ve found having clarity about how the world works comes in handy.”

So can anyone follow her plan? “I believe that you’ll be on track to do more with your life if you first work out what really matters to you, and then expect more of others around you,” she says.

• Drop the Ball by Tiffany Dufu (Penguin, £14.99). To order a copy for £12.74, go to bookshop.theguardian.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min. p&p of £1.99.