I don’t remember my first baby’s last nap. I don’t remember the last time I pulled down her blackout blinds, gave her some milk, lay her sleepsack-clad little body down in her crib and slipped silently out of the room, blinking into the sunlight with two blissful hours to myself ahead of me.

I only know that—like so many things in motherhood—there was a last time, and I didn’t recognize it when I saw it.

Because, shockingly, just as I was at my sickest and most exhausted with her baby sister in my belly, my firstborn gave up her afternoon naps. There was no warning, and suddenly, afternoons stretched endlessly ahead as my cranky toddler struggled to make it to bedtime.

At first, I refused to believe it was happening. But no matter what I tried, she would not go to sleep in the daylight hours. For a while there parenting got a lot harder, and oh how I missed those precious hours of silence in the middle of the day!

When my littlest was born, naps became my obsession. Yes, I am that mom. The one who plans her life around baby’s nap times.

Related: Baby Sleep Guides & Schedules

It’s not always easy, especially when there’s a preschooler and her activities to factor into the mix. In fact, it can be downright restricting. In the early days when the baby was napping three times a day, we were all but housebound for several months.

I’m always planning—making sure to smooth the way for her hours of rest. I say no to playdates, coffee dates, lunches and visitors during nap times. And I’m planning even when it’s not nap time—I won’t take her too far in the stroller when I don’t want her to fall asleep, and I avoid lengthy car rides or leaving her in front of the TV in case she drifts off when she’s not supposed to. We opt to play in the park or the garden or go swimming instead.

As I said…obsessed.

But the truth is, whether we openly admit it or not, nap time is actually a lifeline for a mom. It’s essential for our sanity. In these days we spend in the trenches of motherhood, nap time is a refuge.

Related: 4 steps to prep your baby for a restful nap

When they’re tiny babies it’s a time to recover—physically and emotionally—from what our bodies have just gone through.

As they start teething, nap time is a gratefully guarded respite to recoup from the often sleepless hours of the night before.

As they grow and start toddling around, it becomes a kind of “water break” in the madness—a much-needed hiatus from the constant go-go-go of parenting this wonderful and extremely active human being.

No, it’s not always convenient. But convenience doesn’t even come into play when it’s necessity we’re talking about.

When other people need things from me that I’m not able to deliver because I’m prioritizing nap time, I feel guilty. When I can’t join in when friends invite me places, I feel torn. When my preschooler begs me to take her to the park but I can’t because her little sister is sleeping, I feel wretched.

And yet—nap time prevails.

It’s only now, as my littlest approaches the age my eldest was when she gave up her naps, that I feel the ache of another milestone slipping through my fingers and am reminded how truly short this season of parenting is.

I’ve started taking extra notice of our nap time rituals—the way her head fits perfectly into the gap between my shoulder and my jawbone as she drinks her milk beside me and her hair tickles my nose. The way she hooks one leg over my body and clutches her pink rabbit close. The way she sleepily murmurs, “Night, night, Mommy” even though it’s still daylight outside and the way her thumb automatically finds its way to her mouth as she turns to her side to fall asleep.

I will miss all of these things as much as I will miss the silence in the house and the time to myself when nap time is a thing of the past.

I know the day is coming. But until it does, I’m hanging on to nap time—and to my sanity, TBH—while it lasts.

A version of this story was published March 19, 2018. It has been updated.