My two oldest children recently left for semesters abroad: Michaela went to Paris, and Zack to Beijing. I have all sorts of Mommy nervousness about this, but in my heart I know they’ll be fine. They are adults now, at 21 and 20—and not just adults, but capable, responsible, great people.

I don’t know how that happened.

I know that sounds stupid. And it’s not like I have no clue at all. But recently a few people have complimented us on our parenting, pointing to how great Michaela and Zack have turned out. I should be flattered, I suppose, but I know better than to think that my husband and I are responsible for everything about how our kids turn out. It just doesn’t work that way.

There’s all the genetics and biology, for one thing. There’s nothing like having five kids to make it really clear that kids are, well, born the way they are. I patted myself on the back because Michaela would eat anything I gave her, including any vegetable—and then Zack was born and would only eat White Foods and it turned out that I’d had nothing to do with Michaela’s dietary openness at all. Each child has been born with a different temperament, a different passion, a different way of navigating life. I see traces of myself and my husband in them, but they are their own people.

We have done our best to teach them to be honest, hard-working, kind and honorable. We’ve done everything we could to support them while teaching them to be independent. We’ve guided, pushed and comforted. We’ve loved them desperately, every day.

But we haven’t shown that love every day; we’ve screwed up too. We’ve pushed when we shouldn’t have and not pushed when we should have. We’ve gotten plenty cranky. We’ve misunderstood, misjudged and overreacted. With five kids, we certainly haven’t given each the time he or she needed or deserved.

And there are so many other people and factors that impact a child’s life. There are the teachers and coaches and friends and everyone else—there are so many relationships and moments, some of which I’ll never know, that have been and still are part of making my children who they are.

When I look back on my childhood, it’s moments I remember. Being at the beach with my father at sunset. Building dollhouses with my sister. Walking to the store with my best friend. I remember happy moments, sad moments, arguments and hugs. I remember conversations and books and kickball games and tests. I remember falling in love for the first time—and the first time my heart was broken—and my first day at college. There are so many moments, involving so many different people. They are like puzzle pieces, bits that came together to make me.

Thomas Wolfe wrote (in Look Homeward, Angel, one of my favorite books): “But we are the sum of all the moments of our lives—all that is ours is in them: we cannot escape or conceal it.”

We are in lots of the moments of our children’s lives, obviously—but how they see and feel and use those moments isn’t always what we intend or expect, and there are so many other moments that fill up their lives. That’s the thing about parenthood: we can teach and discipline our children, and love them and nurture them, but ultimately how they turn out isn’t really up to us. They make their own puzzle-piece lives.

All we can do is try our hardest, and hope for the best. Which, really, is all we can do with anything in life.

Claire McCarthy is a primary care physician and the medical director of Boston Children’s Hospital’s Martha Eliot Health Center.  She blogs at Thriving, the Boston Children’s Hospital blog, and Vector, the Boston Children’s Hospital science and clinical innovation blog.