Sometimes the most biting truths, the ones that come as the biggest shocks, are the most obvious. You miss them because they are in you, you are breathing them.

For instance, my sister said the other day, speaking of her daughters: “I never had the conscious thought, ‘One day I will wake up and they will be taller than me.’ I knew it, but I never thought about it. Then when it happened I thought, I wish I could go back to yesterday and just be aware that that was the last time.”

I had my own “so obvious I refused to look at it” moment last week. Those kids you’re so consumed with raising to be responsible, productive, independent souls, will someday actually go do that. They will become their adult selves, they will move out and onward and become people you have to make a date to see for dinner.

Of course this is not news — we began saving for college when they were born — but I have refused to look at it. Maybe it is denial. Or maybe it is getting caught up in the demands of today, that tricks you into feeling that your life will always be exactly as it is right now.

In my first year as a mother, I spent so many red-eyed 3am’s rocking my baby in my arms that I felt that that would be my life forever. I would forever hold his entire weight in my arms and absorb the rhythms of his body in my heartbeat.

It’s all I can do now to remember that feeling.

So last week the realization that time is passing grabbed my face in its palms. It forced me to look at it. My sons are 11 and 14, which translates to “we have time, but also, not so much.” That infant is in high school.

What prompted this realization? A jokey conversation we had about how much my teen is going to love living on his own, doing what he wants, watching football all weekend uninterrupted. The next morning, I woke as though remembering bad news, recalling that conversation. Then I came downstairs with a different attitude toward making breakfast and packing lunches. It’s just a short time more. It’s just a short time more.

It was the same lesson I learned in that dark bedroom, the first year of his life: “This is finite. Be in the moment.” It settled me down, reminded me that the bad and the good of it were not forever. Life’s plans would catch up to us. Mothering babies taught me to be in the moment like nothing before or since. It’s part of why that first year felt like it lasted so long. Each day had more in it.

That’s all I want now — to elongate the days together. But staying in the moment is harder with bigger kids. The days race by. They play on their own. They want their own space. I try to stay close. I offer a back scratch. I look at them and wonder if today is the last day I am taller than them.