My teenage daughter backpacked alone through Europe. Despite my worry, I'd let her do it again.

• My oldest daughter took a gap year when she was 18 and delayed her college start.
• She told me she wanted to travel through Europe for three months with her own money.
• I worried every single day she was gone, but I also needed to trust my daughter.

I was a very fearful child who grew to be a fearful adult. It was so hard for me to let go of that fear while raising my five kids.

The world was full of danger, and I constantly worried about my family. Luckily, the children grew up safely, but I still dreaded possible tragedy lurking just around every corner. I knew mine was not a healthy attitude, and I tried hard to hide my anxiety from them. I never interfered with their steps toward independence — riding a bike to middle school, beginning to drive, finding their way around the city—but my heart was always in my throat. It was an exhausting way to live.

When my youngest child, Julie, was 18, she took a gap year between high school and college. She'd been working and, with her saved money, Julie wanted to travel solo through Europe for three months. While I fervently hoped it was just a passing phase, it turned out that Julie was totally serious.

She presented me with a detailed itinerary and her plans to visit 11 countries. She would stay mostly in youth hostels. My first impulse was to discourage her, to point out all the pitfalls and perils of such a trip. But then I looked at my bright, level-headed girl, who was asking me to trust her. I took several deep breaths and then said, "Yes."

It was really hard to say goodbye

Seeing her off from Newark, NJ Airport was really difficult. She was so excited, wearing a backpack that looked almost as big as she was. Her first stop was Rome, where she attended the baptism of the twin babies of some favorite babysitting customers who had Italian family. That was a gentle way to ease into her journey — at least she was with friends, with a lovely place to stay.

I knew things would not always be this smooth, and they weren't. Julie got lost in the confusing streets of Venice, endured a night in a shady Budapest hostel, became very sick with strep throat, and had to find a hospital in Vienna. But there were so many joyful experiences, too. She was able to visit our former exchange student in Luzern, Switzerland, and her brother Patrick, who was studying in Marburg, Germany. She even went to Finland for her brother Sheridan's violin concerto premiere.

I had to learn to trust her

I continued to worry daily during those months, but I had to learn to let go and trust my daughter. I also had to trust that the world was not the terrible, dangerous place I had always imagined.

Julie and I communicated via a quick daily check-in on WhatsApp, and she regularly sent photos of her adventures. I was reassured to see her smiling face at a restaurant in Florence, on a mountain in Salzburg, in Prague's Old Town. Everywhere she went, she met kind and friendly people. When Julie checked into a hostel in the evenings, she'd connect with a group of young travelers staying there. They'd venture out into Paris together to see the Eiffel Tower glowing in the darkness, and I knew she was safe.

Julie returned home a more mature, confident and happy person. She went on to live in New York City and attend college in Brooklyn, and she remains a New Yorker to this day. Do I still worry about Julie's solitary walks to the subway? Of course. But I remind myself that this girl has proven herself to be sensible, independent, and very resourceful — and I credit her time abroad for a lot of that.

During those three months, I learned a very important parenting lesson, but it's also been a lesson for me. Julie's experience taught me to relax a little, to let go of things I cannot control, and to try, always to look for the positive side of people and places. To see the world as more beautiful than terrifying. I'm still not a big risk-taker myself, but I no longer panic when one of my kids has a daring adventure.

I've asked myself: If I had it to do over again, would I still let 18-year-old Julie travel alone through those 11 countries so far from home?

In a heartbeat.