What if you could do a parenting internship before becoming an actual parent? Imagine it: You’d take your baby home from the hospital with a bunch of diapers and formula samples, along with some experience.

Such an “internship” exists. It’s called working as a nanny. In many ways, it’s an excellent way to develop confidence as a parent. Marilee O’Connor, mom of two, says the years she spent nannying were invaluable. As a nanny, she says she “met the parent [she] wanted to be and the parents [she] did not want to be” and that overall, she had a sense of what having kids would be like.

Jessica Ziegler on the other hand, says that though her nanny experience gave her the idea that she had the parenting thing “dialed in” she quickly learned her confidence was misguided. Ziegler, now the mother of a 13-year-old son and the illustrator of The Science of Parenthood, had worked for one family for three years before starting her own family.

While most nannies agree that their work experience was useful once they became parents, there are certain aspects of parenthood that nothing could have prepared them for.

1 | The sleep deprivation

Even the Navy Seals can’t tell you how to prepare for prolonged sleep deprivation. Not surprisingly, all of the women I talked to found themselves blindsided by the fatigue of new motherhood. Ziegler recalls being completely unprepared for the way motherhood interfered with her sleep – and for how long it took before she felt well-rested again. She recalls feeling “out to sea” during the early weeks of her son’s life. She also recalls, “I didn’t catch up on sleep until my son turned three.” Even Stephanie, a Boston mom with over 10 years of nanny experience, including sleep training says, “I did [sleep training] a lot with nanny kids but couldn’t do it until ten months with my own.”

2 | The baby phase

Many nannies said they were not prepared for the intensity of the early months of their first baby’s life. While many specifically mentioned breastfeeding as something totally foreign, many also remembered more generally, the feeling of being the only one their baby wanted. Lindsay Romero, now the mom of a one-year-old and a speech-language pathologist, says though she felt nannying gave her a pretty accurate picture of family life, she was not prepared for what she described as her daughter’s “constant need to be held or taken care of.” Moreover, she didn’t anticipate that she would be the only one her daughter would want in those moments. Romero says, “Moms are usually the ones kids want so as a nanny they are less clingy and fussy.”

Ziegler recalls struggling with postpartum anxiety, which she says she “didn’t even know was a thing” until she experienced it.

3 | The pressure

Over time, kids’ needs tend to grow less physical and more emotional. However, those needs can be just as intense. Now a writer, a teacher, and a mom of grown children, Mary Lanzavecchia nannied for the same family for three years before starting her own family. She explains, “the stakes feel higher” with her own kids “[because] you are helping grow a person into a functioning, valuable, and contributing member of society.” But as much as we try to be role models for our kids, we inevitably miss the mark. Says Lanzavecchia, “There are few things that feel more frustrating than seeing the not-so-desirable aspects of yourself appear in your child.”

4 | The Tetris calendar

Former nannies find that the stress of a parent’s responsibilities is felt not only in their hearts and minds but also in their schedules. Lanzavecchia recalls being blissfully unaware of all the “extras” she’d have to fit into her day as a mom. “As a nanny, there were so many jobs I hadn’t considered that would be a part of mothering such as the laundry, doctor’s appointments, grocery shopping, and all night vigils when a child is sick.” Ziegler also recalls taking the ability to schedule appointments and errands during her time off for granted before becoming a mom.

5 | The heart-stopping-chest-exploding love

More than one nanny-turned-mom described her feelings for her own children as magical – regardless of how close they were to the children they cared for professionally. O’Connor nannied for years before having her own children and even named one of her daughters after one of her charges. She says though she would “do anything” for the kids she nannied for, “having my own children took it to a whole new level I cannot qualify or quantify in words.”

Stephanie, the Boston mother and nanny agrees. Despite her vast experience, she says, “Even though I loved my nanny kids as much as possible, it is most definitely NOT as much as a parent. I thought it was close but I was wrong.” Along with that heart-expanding love you feel for your own child comes the heart-crushing pain of seeing them hurt, as Stephanie discovered only when she became a mom. “Yes, I was sad to see my nanny kids hurt or upset but I still had a disconnect since they weren’t my own. Also, I didn’t realize how much your child holds your heart and how their cry and being upset just breaks your heart so much more than you ever thought possible.”

6 | The messy intersection of theory and reality

We all know exactly how to parent before we become parents ourselves, am I right? O’Connor remembers thinking, “I was never going to give in to whining. I was going to always be patient. I was going to actively play with them all the times for all of the days. I was going to follow through with everything.” That was, of course, before she had kids. As a mom, she says, “I sometimes give in.” Not only is O’Connor more lenient on herself as a parent, she is also more forgiving of other parents. Where she used to wonder why other parents lost their tempers in tough situations, now she asks herself, “What the hell has your child and adult life put you through today?” with the understanding that she doesn’t have the whole picture.

Stephanie echoed that sentiment, saying that as a parent she is “more understanding of why parents do (or don’t do) certain things.”

When it comes to parenting, no one has a road map. And when it comes to certain things, even those of us who had the opportunity to complete an “internship” are winging it too.