Two days ago, my youngest child turned one. I never thought I’d be the mom who cried on my daughter’s birthday, but there were a lot of things I never would have imagined doing, before. That’s what becoming a mother does to a woman: it grabs hold of the person she was, or thought she was, it tears that person apart – yes, literally – and it rewrites her.  What had seemed impossible in her old life suddenly seems possible – for better or worse- to this new, revised version of herself.

But here’s the truth: this wasn’t the first time that I’ve dissolved into emotional anarchy on my child’s birthday. It happens every time, and why? Because I want to have three children ages five and under FOREVER? Uh, no. Not particularly. Because my understanding, when I gave birth to these girls, was that they would stay tiny and manageable, like miniature dachshunds? Cute, but no. Because the thought of finding a place in my house for all of their birthday gifts threatens to bring on a bout of long-dormant vertigo? Well, yes, but that’s not exactly it.

What is a birthday, to a mother? It is the finality of a year. It is the passage of 365 individual days, one indistinguishable from the next, the way the cars of a train or the dashed lines on the highway blur together as they speed past. I admit that in some ways, a birthday feels a little like grief. Where did a year go? What was I doing? What if I can’t recall all the strides they made, every little way that they grew and changed? Where do those memories go when they aren’t hoarded like treasures?

A birthday, to a mother, is a mad attempt to remember it all. It is the realization that we cannot remember it all, that in the past year the compartments of our brains have been gummed up with sleeplessness and shopping lists and frustration and perhaps one too many glasses of wine. Not everything that should have stuck, did. We see that as our failing. A birthday is a reminder that not every memory is going to stick, that most of the days we have with these beautiful human beings will simply be lived, not preserved. But a mother has a hard time letting go.

These feelings of wistfulness and regret do not diminish the sense of celebration, the joy, the desire to make our overwhelming love known to our child on this day, of all days. No, this is something else we learn quickly: that motherhood is all of it, at the same time, a big soup of loss and pain and love and pride. Our children grew inside of us and we brought them into this world, where they will continue to grow, apart from us. One year at a time.

And while we might wish- as the candles flicker on the cake and the cameras flash and everyone smiles wide- that we could make time stand still, ours is not the wish that matters, today. So we put it away. We smile wide, we live in the happiness of this moment, and we try to hold on to all we can of it, because we are mothers, and we cannot help ourselves.