Just a few weeks after my oldest was born, exhausted by sleepless nights but ecstatic with newborn-baby-love, I phoned my mother.

Mama!, I blurted. Mama! I didn’t realize you loved me so much!

“Well, yes,” she replied in her matter-of-fact way. “So now you know.”

Now I know, Mama. Thank you for loving me this way. I had no idea.

“You wouldn’t. You can’t. No one can know what it means to love a child until they have one.”

And my mother, being both wise and blunt, left it at that. She knew that I had finally gotten the point. And I’m still getting it; I’m still thanking her, though she’s now unreachable by phone; every pang of love I feel for my children takes me back to Mama’s love for hers.

“The umbilical cord is stretching,” she used to say. “It never actually breaks. Just stretches.”

It took me a while to get that one, too. Then I left my baby in a crib the first time. It stretched. Then I left her, howling, with a sitter. It stretched. Then I took her to pre-K, mussing and kissing her sweet head before leaving the room. How it stretched! Then grade school, then middle school, then high school, then a gap year in Ecuador, then college.

Ow.

It’s been the same with all three babies. If you do your job right as a parent, they leave you. What a plain and unavoidable paradox that is, and how important. Today, hugging my second daughter goodbye at the airport as she flew off on her latest great adventure, I felt a tugging at my belly that almost ripped me in two.

But I knew it wouldn’t. I knew the cord, made from the bracing yet bendable steel of maternal love, would neither snap nor wound us. It can’t; it can only strengthen both mother and child, taxing my midriff but tightening our bond. And it will never break.