I know how to time travel. I do it all the time. Backwards: I see a spot on the sidewalk near my home and remember a morning more than a decade old, when I sat down, pregnant and exhausted, to wait out a three-year-old’s tantrum and cry my own tears. Forward: four more years until my firstborn goes to college.

Then what you want to do is close ranks.

You want to hold your growing children close, and you want to do more than freeze time, you want to push time backwards, squish them back to being almost 4 and 7, and not almost 11 and 14, and yourself not 46. 46! You want to hear only their giggles, not their fights. You want to hold the best moments, the photo of them jumping from bed to bed, the older son catching the younger, airborne and naked and laughing. You want to thread yourselves together, beads on a string — mother-father-son-son, the four of you only, connected and always.

And then you want to do the right thing. You want to say to the mother of the girl who is alone, I will take care of her, of course I will. She can join us, she can break our circle, let the beads fall off the string, rearrange them. And so you do, and you grieve for what you think you’ve lost. And you marvel at the new design, different, but not lesser. And you try to hold the present.