It was a day I didn’t see coming. And, yet, I’ll never forget the day I completed my oldest child’s baby book. Yes, this happens. It will happen for you, too.

The day the baby book was completed, I filled out the page for her first day of kindergarten, lovingly attaching the requisite picture of her standing outside our front door, backpack strapped on, eager to get the day started. I noted who her teacher was, the name of her elementary school, how proud we were of this big step…

And then I turned the page and realized… That was it. The baby book was done. It seems so obvious now—of course at age five the baby book is done! Babyhood is over!

But it had somehow never occurred to me during all those years of filling out the baby book that one day the baby book would be finished.

It sounds so silly to say I somehow did not see the end of the baby years coming, but I didn’t. It shocked me that as I slogged through endless days of teething and toddler tantrums and potty training that the days passed as years. I felt robbed! I remembered all the times I thought to myself, “I just need to get through this day.” I did. But as I was getting through days, I was getting through years as well. No, no, no I thought—I never intended for this to happen.

I’m a documentarian by nature. I write down all the minutiae of daily living—overheard conversations, strange sights, things of beauty and also things of sadness. When I finished the baby book, I thought, “What now?” I had nothing left to document. And it occurred to me that a baby book demands to be filled with milestones. The first food, first steps, the first vacation, first day of preschool. All of these matter, of course. They are the touchstones by which we measure growth. They are notable markers of our children unfurling and becoming people.

But what of the smaller moments, the tiny things that are so often forgotten but that are the truest markers of our existence as a family? As I flipped through the baby book I smiled at the milestones, but wondered at what I had let slip through my mental sieve along the way. What small incidents of note and quiet achievements had been lost because I’d never thought to record them?

This fear, this grasping panic at how much good had already happened and could never happen again, impelled me to begin the natural continuation of the baby book: the day book.

My weekly planner suffices quite well for this purpose: I log our appointments and events on the monthly calendar page. And in the lines of each day’s spot on the weekly spreads, I log our life. In these pages, we keep track of no milestones, no particularly special events. In these pages, we keep track of what life is like with small children—the small, terrible, beautiful, wonderful things that define our life as a family. Funny conversations, like the time my oldest child accused me of cooking skunks for lunch when I made Indian food. Minor trills of pleasure, like discovering my youngest had a particular affinity for blueberries.

Some days, I have so much good stuff to write down that I make my handwriting small and cramped and still I overflow the allotted lines for that day. Other days, the hard days, I may have only a line to record, and it might have taken me several minutes that day to think up that one line.

But that’s the beauty of the day book: It forces you, even on the hard days, to find something good about that day to write down.

The day book on these days becomes a gratitude journal, a reminder that each day holds some moment worth remembering. I flip through the archived planners now from time to time and smile at the small moments I would otherwise have forgotten. It is the most accurate and realistic artifact of our life as a family.

I feel certain when I am old and gray, cataracts clouding my vision, weak and frail where I was previously hardy and lithe, these are the days I will return to again and again in my mind. The days when we were young, and the hours were full. The days when we were a family.

In my children’s baby books, I dutifully recorded the well-defined markers of growth. The Big Moments. In our day books, I recorded the smaller moments. The time they correctly pointed out foxglove. The time they got over their fear of the big slide at the playground. The night we ordered pizza and watched Ghostbusters together.

I hope they read these books one day and notice how much I was watching, how much pleasure I took in seeing them become the people they would become. We all deserve to be seen and known in our finest moments by someone who loves us.

Keep the baby books, mothers. They serve their purpose well. But when the day comes for you that comes for all of us, the day the baby book is complete, restart your documenting anew. Record the days. Years from now, you’ll be able to select a year from your shelf, turn to a week, and relive your Tuesday. Oh, you’ll think. I remember that. How sweet that was. These are the things that happened, and they were good. These things were good. And they happened to us.