I see how it feels so easy to just say no to kids. Having kids is irrational. They do not make us happier. They disrupt the halcyon days of early marriage. And they cost a lot of money.

Pretty much every twentysomething says, at some point, that they don’t want kids, and in 97% of those cases that twentysomething is delusional.

Of course there is a biological urge to have kids – but it turns out it’s actually a drive to have sex, not so much to have a baby. So what, then, makes all the people who say no to kids in their 20s end up saying yes to kids in their 30s? Here’s what I think:

There are only two choices in life: career or family.

You can look at anyone in the whole world who you admire, and you can see they picked either career or family. There are not people who have an amazing career who also put their family first.

Amazing careers come from incredible focus and dedication. That singular focus means you are able to also surround yourself with singular focus. The people who are insanely driven to be high performers in their chosen career do that to the exclusion of pretty much everything else.

You are not someone who is going all out at work.

I know this because those people are not reading this post. They don’t care about this topic.

Anyway you know by the time you’re 26 if you love to work. Because 26 year olds who love to work have been working nonstop at a singular, focused goal, since they were 21. Really. Not kidding. Read about Sara Blakely.

If you are 26 and you are not currently exhibiting the drive to meet difficult, all-consuming goals, then you will not have a particularly interesting or fruitful career. Because the careers that are fulfilling are ones you give yourself to.

Just like everything else in life: you get what you give.

The stuff you want in life does not take a lot of time.

Look at people who are 40 years old. Or 50. What are they doing with their days? Probably dealing with family. What do you imagine you will be doing all day, with no kids?

Writing a novel? That takes an hour a day. Doing yoga? That takes an hour a day. Travel? For what? 80 years? At some point you are not traveling anymore, you are homeless.

This is all to say that everyone’s life needs to be about something. Without a career or family the days are long. On the other hand, either a big job or kids can easily consume an entire day.

So there is your big job OR there are kids. I don’t see a choice in life besides career or family. There is nothing else with enough weight to matter in your life.

This is why people don’t take women at 26 seriously when they say no to having kids and don’t already have something big and meaningful that they’re doing instead. What those women are really saying is they thought they would do something big and meaningful with their careers before they had kids.

But look. Everyone thinks that and it’s only true for like 5% of the world. And besides, no big career was built in four years, and that’s when you’d have to stop with the career to start focusing on kids instead.

Let’s be real. The more you put off having kids waiting for that big and meaningful thing to pop into your life, the more you mess up your chances of even being able to have kids.

Having or not having kids is a false choice.

If you want two kids, scientists say you should start trying at age 27. That’s a tough reality. And it doesn’t leave a lot of room for choice.

Women have a biological clock. They are literally going to miss out on having their own kids if they don’t do it soon enough.

Everyone who has kids says they love their kids more than anything in the whole world. It’s hard to say, in the first quarter of your long life, that you want to give that up. So women just have kids.

What if you don’t? The real thing keeping you from having kids is that you think no one will admire you for your brains and ambition. And this is probably true. This Tumblr post summarizes the problem well. It’s not just that most women are doing the caregiving and that it’s unpaid labor. It’s that it puts your life on a path for low performers:

“The more women care for others, the less care they can receive in return, because they devote less time to waged labor than men and many social insurance plans are calculated on the years of waged work done….Because of the devaluation of reproductive work, practically everywhere women face old age with fewer resources than men, measured in terms of family support, monetary incomes and available assets. Thus, in the US, where pensions and Social Security are calculated on years of employment, women are the largest group of elderly poor and the largest number of residents of low-income nursing homes…because they spend so much of their lives outside of the waged workforce in activities not recognized as work.”

But nothing is going to change that any time soon. The only thing that is changing right now is your fertility. And it’s waning.

Competent parenting begets a child who wants to be a competent parent.

I have no data for this except the hundreds of women I coach who say they don’t want children. I’m going to go out on a limb and tell you that almost every woman I coach who did not have kids wishes, by 40, that she did. And I have never met an adamantly childless woman at 40 who did not have a very, very difficult childhood.

When we have no model for being good parent it’s hard to believe it is possible to be a good parent. But the worst thing you can do after your parents ruin your childhood is to let your parents also ruin your adulthood.

So, for those of you who have a career that you live for, kids could ruin that, and maybe you don’t want that to happen. For everyone else, if you are thinking of not having kids, and you don’t have a career that you live for, you’re not being honest.

This harsh reality is true for both men and women, but men have so much longer to live in delusion of a just-around-the-corner amazing career. Women have to face reality much sooner because of biology. Life is about career or kids. That’s it. There are no other choices. You can spend your whole life trying to balance those two things that are extremely important to you. But don’t risk spending your life having nothing that is extremely important to you.