If you are the parent of a child under 18, chances are you've had one or two moments -- maybe even 2,000 moments -- when you've wondered how you're going to keep your sanity until your kid reaches adulthood.

This doubt creeps into the crevices of parents' minds like Georgia kudzu. At the oddest times, too.

During a 4-in-the-morning feeding, say, when you're so tired you moo instead of coo.

In the middle of any show on Nick Jr., which you're sure is never, ever, going to end.

Or when your teenager has just crossed every line you've ever drawn just to see if your head will explode.

It's amazing, really, how entertaining we parents become once puberty takes our children hostage.

I was downright hilarious, I'm told.

Smart alecks.

If you're as lucky as I was when my kids were young, you have at least one older, wiser friend who is willing to pull you aside in the heat of exasperation and assure you the day will come when you will miss every last minute of this mayhem.

In case you don't have that friend, I am here to tell you: It is so.

As for my being here, that's why I'm feeling a little mopey.

I'm not supposed to be here. I should be hundreds of miles away in Providence, R.I., where my daughter is celebrating her first birthday without me.

"You just saw me a week ago, Mom," she said over the phone last week. "And you're going to see me again next month."

When did she get all logical on me? And what could logic possibly have to do with me, her mother?

Twenty-four years ago today, a nurse placed a little baby girl on my chest. Almost immediately, she lifted her tiny head and stared into my eyes, as if to say, "Huh. So, this is you."

Less than an hour old, and she already had me worrying how I would ever measure up.

The nurse patted the crown of Caitlin's head. "Well, look at you," she said, laughing. "Don't you know you're too young to be doing that?"

It is the theme song for our relationship. She is relentlessly her own person. Always loving me, often confounding me, never afraid to take me on.

Me. Her mother. I mentioned that, right?

One of my favorite photos of Cait is at age 3. She is standing with her hands on her nonexistent hips, staring straight into the camera after I'd asked her repeatedly to take off her big brother's beloved sweatband. She had swiped it from his bedside while he was showering, and claimed it as her own.

My teenage son screamed: How? How could I ask him to live with such a thief?

"Caitlin," I said, "take off your brother's sweatband."

"No."

I put my hands on my hips. "Cait, take it off. Now. "

"No," she said, and then imitated my stand.

By the time she was 14, she had already become an expert at throwing my words back at me. Don't you love how they do that?

"You're the one who taught me to speak my mind!" she yelled from across the room. "You're the one who said I should give my opinion!"

Grrrr.

"Not with me," I shouted back.

Golly, I miss those fights.

You know what else I miss? Her stack of flip-flops by the door. Why did I ever complain about that? And the way she left the bread bag open.

"It's going to get stale!" I shouted.

"OK!" she shouted back.

I even miss the stress. All those nights of changing my clothes in the minivan as I raced home from work to coach her softball team. I never felt so needed.

I miss that stupid van, too. Or maybe what I mean is, I miss the reasons I needed one. I was the car-poolin' mama, back in the day.

Listen to me. Pathetic. I have a great life. As an editor friend once scolded, "No whining on the yacht."

Ouch. Point taken.

Overnight, it seems, my baby girl went from a gangly 13-year-old hiding behind a curtain of hair to a confident young woman bent on trying to change the world. Or at least her patch of it, which right now is full of underprivileged middle-schoolers.

"My kids," she calls them.

Once in a while, one of them slips and calls her "Mom."

Oh, my.

I sure do miss my kid.

So, I'm just here to warn you, dear parents.

One day, you will, too.