I think the No. 1 thing I was least prepared for about parenting was just the sheer physicality of it. I mean, I knew I wouldn’t sleep, but I’m an anxiety-ridden insomniac at the best of times, so not sleeping doesn’t bother me as much as it bothers a lot of people. If anything, I think I enjoyed Ruby’s infancy because nursing and snuggling a baby at 3 a.m. beats lying awake listening to the clocks tick and the faucets drip. And because I have been a loyal reader of Parents magazine ever since I was 12 – the family I baby-sat for had a subscription – I knew all about the various ways to combat diaper rash, alternating Tylenol and Motrin for teething babies, strategies to stop a tantrum in its tracks, the 10 things you need in your first aid kit, pool safety and how to pick a summer camp. I was ready for all of that.

I was not ready, however, for the extent to which, once she was out, Ruby would still use my body as an extension of her own. Boundaries just don’t exist anymore: Yesterday, Ruby picked the lock on the bathroom door, walked in, announced that she had to potty, pulled down her Tinkerbell panties and sat in front of me on the toilet in much less time than it took you to read that sequence of events, too fast to even stop her before I realized what was happening. Tandem peeing is not something I am exactly comfortable with – and we talked afterward about her not doing that ever again – but honestly, I have so little concept of personal space these days that it didn’t really faze me. And this morning, while I lay back to wash my hair in the tub, Ruby kneeled at the side and draped a white washcloth over my left knee, declaring it the bride, and then wed it to my right knee in a quickie ceremony that was over before I even put conditioner in. Yes, my knees got married this morning, and I was naked when it happened. She even knocked them together so they could “kiss.” Welcome to my life.

When we watch television, she treats me like a chair, her back against my chest, her legs – longer every single day, it seems – hanging down against my own. When we take walks longer than a block or so, she treats me like a car service, begging to be spared the indignity of using her two perfectly good feet (even though she is two-thirds of my height already, and I look ridiculous carrying her). When it’s bedtime, she treats me like a body pillow, carefully arranging my limbs in the most pleasing and comfortable configuration for her.

The hand-holding, the hugs, the kisses, the cuddles, the way we know each other’s most ticklish spots: It is at once the most innocent and most intense intimacy I have ever experienced. I know every single centimeter of Ruby’s body from the mole on her left instep to the birthmark on her right hip to the freckle on the very tip of her perfect nose. She is closing in on 5 years old, and I am still amazed, almost daily, by the fact that I made her – her ears, her fingers, her gorgeous greeny-hazel eyes, her tiny little belly button that hasn’t quite decided yet whether it’s an innie or an outie.

There is a lot you can learn by reading, but there are some things that you only learn by doing. And in this, the physical aspect of parenting is like any other physical thing. Reading about running or playing volleyball or swimming is one thing; actually doing it is quite another. (I assume it is the same with other physical sports, but these are the only three with which I have even the slightest experience, and no, I am not good at any of them.)

So yeah, pre-baby, I knew, thanks to my obsessive reading, about baby-proofing. I knew how and when to introduce solids. I knew a lot about cloth diapers, sibling rivalry, insect bites, sunscreens, how to pick a good family dog.

Basically, from the reading I did pre-baby, I knew what kind of thermometer I should buy. But post-baby, I could look at Ruby and tell by her eyes if she had a fever; I could tell with a hand on her forehead how high it was.

I have long been an advocate of “book-learnin’” – and I make no apologies for the vast amount of knowledge I have on food allergies (even though Ruby blessedly has none), warning signs of serious childhood illnesses (even though Ruby blessedly has none) and behavioral issues (um, well, Ruby has a few). But as much as I used to hate people saying patronizingly to me, “You just don’t understand until you have a kid,” it’s true. You really don’t.

What was your biggest parenting revelation?