“I  think I’m going to change my personality when I do my hiking trip this summer,” granddaughter Emily announced to me recently. Say what?

Emily is 13, and 13, I can attest, is a wondrous age − and also an unpredictable one, at least for girls. I know because I’ve been there myself, then with daughters and now with granddaughters.

Thirteen is all about mood changes, anxiety about fitting in, anxiety about looks, anxiety about − well, just about everything. Thirteen is no easy ride.

But back to the personality change.

Emily was born complicated. This granddaughter has always questioned just about everything, from why God allowed the Nazi Holocaust to how time was invented to why one side of her hair curls up and the other curls down.

And that’s all part of being 13. The profound, the foolish, the questions to which there are no easy answers start to surface. Being 13 also means alternately feeling goofy and acting it and, just as surely, feeling omnipotent.

“I’m really, really good at spelling,” Emily confided. But then she adds that only her best friend knows that because, well, it may not be cool to be good at spelling. So much for the omnipotence.

I have watched Emily move from chubby little sparkplug to slender fashionista to bewildered consumer who is virtually paralyzed when she has to decide on an ice cream flavor. Like so many her age, she wants to experience everything there is. Why settle for chocolate when cherry vanilla also beckons? The indecision over ice cream flavor is a metaphor for so much more.

Emily has been thinking about why her paternal grandfather died. He was, she reasonably points out, a doctor who saved lives. Why couldn’t he save his own? In her 13-year-old head, that just doesn’t compute. And while I’m many times her age, I have pondered that too.

I love 13-year-olds for exactly these reasons. They are incredibly provocative, profound thinkers who also fall apart at the notion that they look fat in certain jeans. I taught 13’s decades ago, and aside from motherhood, it was my toughest job.

Once I brought in a Picasso print to our language arts classroom and asked the students what was going on in a portrait of three people looking out at the sea. The kids almost all decided they were a mother, father and child − and then all bets were off.

I remember how their leaps of imagination fascinated me and terrified me and left me speechless. They saw more in that simple painting than I ever had.

I thought of all that when Emily and I walked on the beach  when she was still 12. We looked at the ocean, and she told me how she sometimes imagines floating on soft waves and letting her problems just disappear under those waves.

“Your problems?” I asked her. I should have known better.

Kids worry about things they don’t share. They may cry into their pillows at night and never tell us, and certainly never tell us why.

Perhaps a glitch in the ongoing soap opera with her best friend of the week? Perhaps worries about how hard eighth grade math will be next year? Whatever makes this girl-woman I love so fiercely passionate or angry, giddy or terrified, she is already past the point of sharing everything.

I loved 9, when Emily was all revelation. Ten was wonderful too, when we would talk thoughtfully about books she’d read and then relentlessly about why she so desperately needed a cell phone, an argument she finally won with her parents this year.

Lately, I’ve been trying to spend more time alone − just the two of us − so I might get a glimpse of what’s coming next as the double-digit birthdays march on. I suspect I’ll stand on the ground looking up at this high-wire tightrope walker who is my granddaughter. I’ll try to be as brave and strong as she is. But I know that sometimes, my heart will be in my mouth. Because there is nothing quite as challenging as letting baby birds fly free, even when you know nothing can stop them.