I take a handful of sand and watch the granules gradually slip between my fingers.

My 1-year-old digs in the sand, then puts the yellow plastic shovel in his mouth. I chuckle at the grimace on his face and dust away sand from his lips.

It feels like yesterday my oldest boy had the same wispy blonde hair that turned platinum in the summer, sweet dimples on his hands and knees. Now, his hair has darkened and his legs have lengthened. And somewhere along the way, he stopped calling me Mommy, switching to a simpler Mom. I didn’t even notice until months later when he called me Mommy, and I realized it sounded strange because I hadn’t heard it in a while.

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All signs of growing up, just like he’s supposed to. That big-yet-still-little boy got on the school bus this morning, waved with a smile, and sat down—ready for his new adventure at kindergarten.

Another grain of sand slips through my fingers.

Yes, I am a bit sad about him growing up even though I’m excited for all he will learn and do. I miss the sweet baby voice, squishy toddler cheeks, and the way he said, “Oh no!” with such 1-year-old drama. But this summer he learned to ride his bike and write his name. He tells me he loves me and I’m the best mommy in the world. He makes amazing connections and I love to hear his insights.

Some little kid bits remain: he still skips the number 15 when counting to 20. He no longer sits on my lap but loves to squish up next to me and spread a blanket over both of us so we’ll be cozy. And there’s that small section of hair, blonder than the rest, that reminds me of the baby he once was.

As I’m letting go of this little kid and watching him become a big kid, it creates a swirl of emotions. Every new triumph brings just a bit of sadness, like the pinch of salt in a recipe filled with sugar. He doesn’t need the training wheels anymore, he’s outgrown all his little kid toys and clothes, the board books were passed to his brother.

More sand slips.

It doesn’t help that autumn is around the corner, its subtle hints reminding me that summer is drawing to a close. It’s still warm, but I can see hints of change: the twinge of red at the very top of our sugar maple. A few yellow leaves prematurely drop from our Big Old Tree. I look at it and realize it’s not as full as it was in June. When did that happen?

Another year wrapping up. Another grain of sand slipping through.

Sure, summer will come again, and that hope is what keeps us warm through winter. But this summer won’t come again. This last summer before my big kid started kindergarten. This summer when my little baby turned one and went from crawling to standing to walking. This summer will soon be a memory, sand that slipped through. And so, I cherish it.

I love autumn, but it always reminds me that the long summer days are fleeting; time is moving forward whether I want it to or not. Before I know it, I’ll be sending this little sand-eating blondie in front of me off to preschool. It feels so far away, but so did it with my first and, somehow, two years of nursery school went by in the blink of an eye.

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I drove by the preschool the other day. Seeing the building and play yard, realizing it’s over for my big kid sent an unexpected wave of melancholy through me. How? How did it go so fast?

Another grain of sand.

But these grains aren’t falling into oblivion—they’re falling into my memory bucket.

The place where I can play when I’m old and want to dig through my memories. When I’m feeling nostalgic I’ll sit in the sandbox, stay a while, and play.

For now, my 1-year-old and I will dig and build sandcastles (or eat them, in his case). We scoop up new handfuls, create new memories. Nothing lasts forever, not tow-headed little boys and endless days at home. Not those painfully sleepless newborn nights and puddles of drool from teething. Brevity makes things precious. After all, would we appreciate autumn if it lasted all year? So I’ll do my best to live right here, in this moment, before the grains I’m holding slip from my hand.

A few tears might mix in, but I’ll smile and pick up the shovel. Because while I’m a bit sad about how fast things are going, I know there’s always something to smile about, new adventures to look forward to, and more sandcastles to build