When my son was in preschool he was asked what he wanted to be when he grew up and he said, “A robot.”

His reply was both absurd and sensible. No, he can’t grow up to be a robot (a cyborg, maybe, though that is a different conversation). But he was answering a familiar question very reasonably in light of repeated assurances that “you can be anything you want to be.” That promise has some roots in democratic pedagogy, since Americans need not grow up to be butcher, baker, or banker just because Dad was. It became more universal after women’s advances in the 1970s; “You can be anything you want to be” became a way of saying girls could be anything they wanted, could be something other than secretary, schoolteacher, or mom.

Of course, you can’t be anything you want to be for all kinds of reasons. In the past few decades, contention over worthy life paths for women has centered on the tension between career and family. But before long the question arose, what do women want? When women were presumed to care most about their husbands and children, demanding work was thought to come only at the risk of detracting from happy relationships. This was a trade some working women were willing to make. More recent backlash hints that while young women embrace education, challenging jobs, positions of power, and superior pay, these do not compensate for the loss of domestic happiness. Our current tentative consensus confirms that while work and family both are attractive and may be possible to have together, women can choose to emphasize one or the other.

Sheryl Sandberg, who blazed a career at the US Treasury, Google, and Facebook, wants women to think about that balance afresh. She wants more women in leadership posts. Her new book, Lean In: Women, Work, and the Will to Lead (Knopf, 2013), makes this case. Much of it presents ­garden-variety go-getter counsel. Commit yourself fully to work you love; worry about smart business moves more than finding a mentor; set your own boundaries for personal life and work; push yourself to participate and exert influence; don’t shrink. It is not gendered advice per se, except that Sandberg anticipates women particularly need it for two reasons. Women need to hear this because their socialization plus lingering inequities predispose them to hang back or defer. And this advice claims a hearing since some conspicuous women in recent years—highly educated and full of potential—have hedged about professional engagement because it threatened to complicate, even foreclose, family life. Anne-Marie Slaughter’s article “Why Women Still Can’t Have it All” in The Atlantic last year provoked controversy over this admission.

This is Sandberg’s particular pique. Sure ladies, she concedes, you someday may want to have a family and someday may need to adjust your job to accommodate it, but deal with that problem later, rather than compromising in your young years when horizons are broad and no babies are in the house yet. Structural hurdles still impede progress, but women should not make things worse for themselves by imposing their own interior obstacles. Sandberg insists that “women can pursue professional success and personal fulfillment—and freely choose one, or the other or both.”

Part of that counsel is fine, as far as it goes. It speaks predominantly to corporate leadership, rather than to the excellence of a particular kind of work. Leadership in the abstract, lacking purpose in where and whom one leads, is a questionable ambition. Of course, some jobs are more suited to flexibility and family boundaries than others, and booming economies are easier environments than fragile ones for the sort of negotiation Sandberg recommends. Plenty of people have jobs that are worth doing but that offer little glamour or professional success: leaning in there might not be so compelling a prospect.

Even in the best cases, though, this prescription is faulty, first in tying identity too closely to paid work, and second in making one’s own satisfaction the primary objective. Vocational imagination is more richly sustained by considering what you do well and what good can be done by doing it, rather than by thinking mostly about what you want out of a job. A job is an important part of life but much less than the whole of it. The I-am-what-I-do equation does not represent a victory for women. A large measure of one’s vocation might include tasks uncompensated or unrecognized. While Sandberg commends volunteering and other undervalued uses of women’s time, she does not offer a way to value them beyond one’s own choice.

Sandberg does not lose time arguing for or against marriage, presuming agreement that a life companion is nice and need not compromise one’s ability to pursue a career. “When it comes time to settle down, find someone who wants an equal partner.” The language is clear here. What is wanted is someone who will be fully supportive of his wife’s work, who realizes that her time is as valuable as his. It will be a partnership of two equals, pursuing happiness not mostly in sharing of lives, but through their independent career achievements. In any case, finding a suitable spouse is not the problem. The crux of the work-life conundrum for women is childrearing. Far from discouraging the combination of career and motherhood, Sandberg thinks it is eminently doable.

But why should we assume the combination is desirable? If women can choose whether and how to work, what is it about children that would make their possibility an attractive choice to a woman launching a career? Family life does not consist so much in personal fulfillment as in self-emptying. Children are good. Taking care of children, even happy, well-adjusted children, is hard. Children break things, wake up in the middle of the night, throw up on you, resist the good, find your being embarrassing. And that is what parents might expect of the easy ones. All of that—and more—might be part of what being a mother to one’s particular children will entail. To admit this is neither to belittle parenthood nor to overlook the pleasure in it. It is to insist that this package, which is fully part of what one takes on when receiving children, is not well described as personal fulfillment. A young woman planning her future and aiming to “choose” children does not think about the choice as that.

One could argue that parenting is not as hard as some women make it. All mothers do not have to do what some mothers do. Making ­smiley-face pancakes and packing lunchbox notes; placing kids in clever activities; matching school outfits to holidays; anointing every knee scrape with antibiotic gel; watching every pencil-scratch of children’s homework: these are components of the phenomenon labeled overparenting. The label is imperfect, failing to distinguish between doing too many extras and simply doing the lot that is needed. It may be that mothers do unnecessary things, the “Perfect Madness” Judith Warner rejects in her book of that title, blaming in subtitle “motherhood in the age of anxiety” (Riverhead Books, 2006). Women may do all this as striving behavior, supplying advantages in hopes that children grow smart enough to have jobs as cool as—or cooler than—their ­parents. Intensive ­parenting also may arise from the redirected energies of bright, able women who, turning from careers, engage motherhood as the sort of project worthy of forsaking a job for. Or they may do it because it is not always clear which parenting tasks can be skipped.

While some parents may overdo it, critics can err in the opposite direction, implying that children basically raise themselves. Or, as economist Bryan Caplan puts it in his breezy nature-over-nurture case, Selfish Reasons to Have More Kids: Why Being a Great Parent is Less Work and More Fun Than You Think (Basic, 2011), parents should ease up since most of what they teach children does not stick anyway. I think some of it sticks. Further, even if children reject some parental directives, their tending, feeding, manners, and moral instruction—to say nothing of education or job skills—require significant gift of time and effort. The gap between childcare and raising children is significant. Childcare is forced to bear a lot of weight in arguments like Sandberg’s, as though what had to be done with children during the workday were simply supervision, keeping them safe and maybe busy. Much about ­childrearing cannot be done during the workday, and parents home after a long shift from work may not have time or energy left to do it all.

Time figures into the very decision to have children, the placement of them in the life course. More than Sandberg acknowledges, biology, as well as choice, pushes women’s decisions. While women ought not be tyrannized by ticking biological clocks any more than time clocks, concern over the inability to have children later does quite reasonably prompt many to seek motherhood first. Delaying childbearing can raise the risk of infertility and compromise the health of both mother and baby. There is some irony in downplaying these risks in a culture so keenly health-conscious as ours.

Sometimes those who write about work and motherhood regret that women do not stick up for each other, that they judge each other’s choices rather than celebrating together the fact of choice. Mutual judgment is not unreasonable, since a life lived according to an opposite choice calls one’s own into question. The accomplishments of a woman like Sandberg, with impressive title and reputation and salary, invite suspicion over the time use of a stay-at-home mother: what does she do all day? why does she deserve so much leisure? why does she waste herself when children clearly do not need what she gives them? And, in contrary, full-time moms—the phrase by itself betrays mothers’ pressures to justify that life—might wonder, if income or urgency do not explain another’s job, why a working mother puts herself and her household through the extra trouble. It is laudable that women have educational and professional opportunities formerly closed to them, but choice carries hardships as well as boons. All choices are not equally good. The fiction that all choices are open—you can be anything you want to be—is misleading, even paralyzing.

“Lean in” as a catchphrase is not so different from “Be all you can be” or “Live Strong.” Amen to all that. But leaning in to corporate success and hoping for the enjoyment of family on the side is a smaller vision than it could be. Young women on the rise might imagine the future in a bigger way. First, take inventory not only of your desires and abilities, but others’ claims on your life and time. Second, avoid defining yourself primarily in terms of your job, whether that job is low or lofty. Third, when marrying, aim to build together a purposeful life in common, rather than the parallel play of boosting independent achievements. Fourth, receive children as blessings of that union and affirmations of embodied life, who call forth a great and unpredictable lot from both parents and who share in family goods. Then lean way in to that.

Agnes R. Howard is Assistant Professor of History at Gordon College in Wenham, Massachusetts.