“Work-life balance is a lie,” according to Thasunda Brown Duckett, president and CEO of the Fortune 500 financial services company TIAA, and she thinks she’s a better mom for giving up trying to give her children 100% of her time.

The Wall Street titan recalled the light bulb moment came after breaking down in tears when another long day at work meant missing out on seeing her children that evening.

“I called my husband and I was like, when I get up in the morning, I don't see my kids,” Duckett told LinkedIn News. “When I get home, I don't see my kids.”

Her husband, who’s an engineer, Marine, and a stay-at-home dad, advised her to simply quit her job. Instead, she said she quit striving to do and be everything, all of the time.

“Here's what I learned: Work-life balance is a lie because I was trying to reconcile it, and the math wasn't mathing,” Duckett explained.

“The truth is I only have 100% of me, not 110%. Understanding that I am not 100% allocated to being a mom, they only get 30%, allows me to be more intentional…So my children don't get 100% of all of me. But within that allocation, they get 100%."

Fortune has reached out to Duckett for comment.

Work-life balance as a diversified portfolio

Instead of simultaneously trying to devote 100% of herself to motherhood and 100% to being the boss of a $45-billion-a-year financial firm, Duckett said that she tries to think of the time she has like a diversified portfolio.

“If you live your life like a diversified portfolio, just like with your money, over time you will outperform,” she explained.

“On any given day, I may not feel like I'm the best mommy when I'm traveling. There's days I don't feel like I'm a great CEO. There's moments I don't feel like I'm a great daughter,” she added. “But over time, I'm a really good mom. And over time, I believe that I'm in purpose as a leader and I'm doing a great job.”

She’s not the first to admit that it’s impossible to give motherhood and a bustling career equal attention—and thrive in both roles.

Whoopi Goldberg has even candidly admitted that it ultimately meant she had to choose her career over her child. Meanwhile, the pop star Lily Allen revealed on a podcast that having children “totally ruined” her career.

Holly Wilbanks, the founder of the Wilbanks Consulting Group, echoed that idea earlier this year to CBS News: “The concept that we can do it all, I think many of us have realized, is not a realistic concept.

“Instead, what women today are trying to do is figure out what’s important to them, what they value, and how they can structure their focus and their time around those things—and quite frankly, for a lot of women, that means making choices.”

Wall Street veteran Sallie Krawcheck similarly outlined that she's had to be thoughtful about how she invests her time as a mother and CEO.

“There were times in my life when I just went, ‘Go, go, go, go’ with the career, and did a perfectly adequate job as a mom,” the founder and CEO of Ellevest said. “But [I] was not that perfect mom with the homemade cookies.”

Likewise, Krawcheck said, “there were times in my life where my kids needed me when the career took the back seat.”

The myth of ‘having it all’

It was Cosmopolitan magazine that came up with the “You can have it all” mantra—the corner office, children in tow, and not a hair out of place.

But even its former editor-in-chief admitted that not only is that unrealistic, it’s also a “very dangerous” norm to perpetuate.

“You can’t do it all properly, all at the same time,” Farrah Storr said when she was still at the helm of the women’s title.

“I decided not to have children—I just didn’t think I could do my job with kids in tow—and that’s been a huge personal sacrifice.”

If even those with huge incomes to chuck at childcare are admitting it’s hard to excel at both motherhood and work at the same time, then what hope does the regular working mom have?

About a quarter of a million mothers in Britain have left their jobs in recent years because of the difficulty of juggling a career and childcare, according to the Fawcett Society.

Meanwhile, women who do remain in the workforce after having children are financially punished: Mothers experience a 60% drop in earnings compared to fathers in the decade following the birth of a first child, according to PwC. 

Over 40% of the mothers the Fawcett Society surveyed had turned down a promotion or career development opportunity because they worried it would not fit with childcare arrangements.

Men, on the other hand, see their pay increase after becoming fathers.

This story was originally featured on Fortune.com