By Monisha Perkash (Co-Founder & CEO, LUMOback)

“You can have it all, just not at the same time.”

These were the words of advice from a well-intentioned mentor who was trying to help me figure out how to pursue an entrepreneurial career and also start a family.

I knew she was trying to be reassuring, but I bristled at her words. To start with, I disliked being told that there were any limits to what I could pursue. Further, I wondered, if your 30s are when a) most people’s careers take off AND b) women’s fertility declines, how could anyone feasibly argue that one could wait? And if men could be family guys and also rising stars in their professions, why not women, too?

Proudly obstinate, I decided to prove to the world, and myself, that an entrepreneurial career does not have to compete with family. I was going to “have it all..”

My journey began with the birth of my first child. Everything about him was wonderful, but I was a different story. Endless diaper changes, chronic sleep deprivation, inability to complete a coherent sentence, and a marked lack of hygiene (if you don’t have time to shower until the late afternoon, why bother, right?)… they were all taking their toll. I needed to engage with the outside world in a meaningful way or risk losing ME. And so I took the plunge by starting my first company.

In my mind, being more engaged with the world around me would make me a better mother and wife. And I’m happy to say that I was right about that. I relish my family before and after a workday because, as they say, distance makes the heart grow fonder.

But there were other things that I got wrong. Like “having it all” doesn’t actually mean that you auto-magically get twice as much time. Yes, I was living my entrepreneurial dream, and yes, I was committed to being a great mom, but I gave up a lot: I barely slept, exercised infrequently, deprived our family of needed vacations, missed weddings and reunions, and completely lost track of anything going on in the real world. I also had to be okay with focusing on quality, not quantity, time with my kids.

So would I do it over again? Yes. But would I do it differently? Definitely.

I would have had the humility to know that I needed a stronger support system.

For instance, I would have built a more diverse founding team, both to bring complimentary skills and to take some pressure off during those days when one of my kids had to stay home sick.

I also wish I had publicly embraced the fact that I was an ambitious working mom. Early in my entrepreneurial journey, a prominent male executive who saw a screen-saver with my newborn’s picture advised me that such a display might cause prospective investors to become concerned about my priorities. As he told me this, I looked over his shoulder and saw his windowsill adorned with pictures of his own children — the ultimate double standard. Do people judge a mother differently than a father? Yes. But those judgments shouldn’t all be negative, and by hiding who I was, I was simply perpetrating the issue. Now, I proudly talk about how my dual roles have made me effective at multi-tasking, efficient with time and resources, and flexible at changing gears. I can also attract more diverse talent to the company, and I understand the enormous spending power of women consumers.

The final thing I would have done differently was to reframe “having it all” as “having what matters most.” And of course, what matters most is different for every person. For me, it is loving my family fiercely and building a great company.

For one woman whom I admire tremendously, what matters most is taking care of her family and home, and being extremely present with her children so that she can guide them through their foundational years. While she’s had the type of training and schooling that qualifies her to run Fortune 500 companies, she’s quite content to keep her priorities on family for now.

For another woman who inspires me, what matters most is satisfying her constant drive to come up with creative solutions to business challenges. She hasn’t been terribly interested in integrating kids into her already busy life, and has chosen not to have children.

For a third incredibly motivated woman, what matters most right now is pushing hard on an amazing career opportunity that has the potential to provide complete financial independence for her family. This means that she works long hours and travels quite a bit, but when she is with her husband and children, they are her undivided focus.

The reason why these women stand out in my mind is because they are all authentically happy. They have chosen to focus on the things that currently matter to them the most, and their personal fulfillment permeates their very essence.

So the words of advice I’d give to any woman, or man, trying to have it all I’d say: Don’t. You really can’t (my mentor was right). But you can have what matters most, to you.

Editor’s note: Got a question for our guest blogger? Leave a message in the comments below.

About the guest blogger: Monisha Perkash is Co-Founder and CEO of LUMOback, a mobile health solution for managing back pain. LUMOback recently emerged from Runway, a startup incubator program backed by Eric Schmidt’s Innovation Endeavors venture fund. Monisha previously co-founded the online college financing service TuitionCoach (acquired by SimpleTuition in 2009), where she oversaw the financing, launch, and general management of the startup. Monisha holds an MBA and MA Education from Stanford, and a BA from Yale.