Exactly 20 years ago this month, I leaned in – big time. I was 29, and during my first maternity leave I was promoted to become the editor of Roll Call, the political newspaper that covers Congress. I spent three years in that job and another seven in various management positions in journalism and PR, both in Washington DC and London. During that time, I had two more kids. I was living the Sheryl Sandberg-Marissa Mayer dream – good jobs in my field, brief maternity leaves, and a husband who did at least his 50-50 share. Like Sandberg and Mayer, I basked in my exhausting, joyfully hectic life. I had occasional pangs of guilt, and wanted to spend more time with my kids, but mostly I felt smug that I had pulled off having it all.

Then, suddenly, things changed. Ten years into the working mom gig, the upstart DC newspaper that I helped found unexpectedly folded. For the first time in 17 years, I wasn't working. I decided I'd take a few months off before I figured out my next professional step. Overnight, I went from Sheryl Sandberg to June Cleaver. And it was an eye opener.

Until I stopped working, I had not regularly picked up my kids from school, opting instead for the early morning carpool, as most working parents do. The first few times I picked up my three-year-old from pre-school, I came to the classroom door and watched his eyes find me in the sea of parents and nannies. Each time, I felt like a rock star – such was the glee and joy when his face lit up and he raced over and flung his body into mine. At first, I figured it was the novelty of my arrival in place of our nanny. I was wrong – it's just how pre-schoolers greet their parents.

A few hours later, I would pick up my 1st and 4th graders from their school. With slightly less airborne contact but just as much energy, they would barrel into the car and race through a breathless description of their day – the classroom, recess, and tales of friends, teachers and special guests. It all spilled out in a matter of minutes. Later that night, when we sat down to dinner and my husband tried to talk to the kids about their day, it went something like this:

Husband: "How was your day?"

Kids: "Good."

Husband: "What did you do at school?"

Kids: "Nothing."

Gone, all of it. By dinner. They had moved on.

For the next few months, I played what I thought was a temporary role as "stay at home" mom – although I wondered if I was doing it wrong, because I seemed to never be home. I was at school, the park, on the soccer or baseball field, in pediatric waiting rooms, at music, skating and dance lessons. Or mostly, I was just in the car.

It didn't matter – I loved being with my kids. In those days and weeks of afternoons together they were growing into the big kids, and eventually, teenagers. They were each more interesting and entertaining than I could have ever imagined. I never grew tired of spending time with them – and I knew pretty quickly I wasn't going back to a big job in journalism soon.

Our afternoons were not always idyllic – we had our share of homework v video game fights, and I'm certain I agreed to more junk food and television than our nanny ever would have allowed. But I was there for skinned knees and middle school angst, championship games won and lost, holiday baking, and math breakthroughs. All the while, I felt a bit of a fraud – because I knew I was indulging my needs. Despite the case that others may make, my kids would have been fine without me. Perhaps it's the journalist in me – I didn't want to miss anything.

At that point, I could have gone back to full-time or part-time work with reasonable hours and some degree of flexibility. But returning to a position in news management – in other words, a job I loved and was trained for – would have meant 60-plus hour workweeks, 24/7 availability, and at least some travel. Such a lifestyle is simply not compatible with regular and consistent involvement in the everyday lives of children, and no amount of leaning in that would change that.

Sandberg and Mayer have young children, so it's possible to leave the office at 5:30pm and get back to work after the kids are in bed. Fast forward to the teen years, and we'll see what happens when their kids are up as late as they are. Hint: some of the best teen bonding comes at night.

So while I agree with Sandberg that women should aim high and play tough – I loved my jobs in management – I do not believe that women's internal barriers are the primary cause of the abysmally low numbers of women in leadership. Instead, I believe the realities of the demands of leadership simply dissuade women from continuing the climb to the top.

The statistics bear repeating: women make up 18% of Congress, 2% of Fortune 500 CEOs, and 9% of directors of top grossing films. But it's not that women aren't working. According to a post-census report from the Bureau of Labor Statistics, entitled "Women in the Work Force", women make up 47% of the total work force and 51% of all those employed in "management, professional and related occupations". And 71% of all mothers of children under 18 are in the labor force. Are these women not leaning in?

It's important that we do not confuse women who work full-time with women in leadership.

Certainly, it is controversial to suggest that women are disproportionately compelled to want more flexibility and more time at home than men. But Sandberg herself recently told an interviewer:

"I drop my kids at school and see the mothers who are going to be there all day volunteering, and they are going to know more about what my child does than I do. I miss being with my kids and I feel bad about that. Dave drops the kids off at school and he feels fantastic that he dropped the kids off at school."

I cringe when I hear well educated, successful women refer to their "choice" to spend more time with kids rather than stay on a high-powered career track. They should never have to make that choice in the first place. Instead, we need to recast the very nature of those top jobs if we want to include the unique perspectives of women at the table and take advantage of an enormous talent pool that is currently, yes, leaning out.

It's a tall order to push back against the work patterns of a highly achieving economy, and I'm not unrealistic; I know the drill from years of living in DC and Silicon Valley. But until we acknowledge honestly that the relentless demands on professional leaders discourage smart and talented women, we will fail to move the numbers significantly for women at the top. That's a loss for everyone.

It will require men to support this effort, since they are the ones who now hold the levers of power. But it can and must be done. In the words of Warren Buffet writing about Lean In for Fortune magazine:

"Fellow males, get onboard. The closer that America comes to employing the talents of all its citizens, the greater its output of goods and services will be."

And let's face it, shifting the expectations for everyone who serves in leadership will also restore balance for men – and fathers – as well. It's a win-win.

I agree entirely with Sandberg that change will come with women working together – not apart – on all aspects of this societal challenge. So in addition to women focusing on their internal barriers, it is crucial that we also meaningfully address structural changes that would make positions in leadership more accessible for all women.

It's a conversation that should include men and women, policymakers and business heads, scholars and smart thinkers, current leaders and those who wish they were those leaders. The discussion should include everything from concrete tweaks – such as job sharing in the highest posts, work hours that track with school schedules, email blackouts, mandatory departure times (in other words, family friendly policies actually implemented in the top posts) – to major cultural and atmospheric shifts that will only come with changed behaviors.

(I will add here the requisite qualifying paragraph that I'm writing about a narrow cross-section of well educated women, who have the financial ability to determine the amount of time they spend with their kids. I'm also not referring to all types of jobs. For some sectors, real change in how work gets done is unrealistic; you can't job share an elected position, for example.)

We're so quick to throw up our hands and declare that women can't have it all, which squarely places the burden of work-life balance on us. What about industry's responsibility to change the definition of leadership jobs so that women (and men) can have it all?

Over these last 10 years, I've tried to stay engaged in life outside of the home. I took roles in our local community, co-founded a non-profit that promotes women in politics, and I worked hard to elect more women to Congress in 2012.

Make no mistake – I derailed myself from the leadership track, and I struggle with how that will impact the next chapter of my story. But I wouldn't trade a single one of those afternoons and nights with my kids if I had to do it again. If anything, I regret the ones I missed.