Whether you’re an introvert or an extrovert, you’ve probably befriended a few people you’ve crossed paths with during your travels. On the road, we have a natural tendency to seek connection, so we often want to converse with locals and fellow travelers. It’s just part of the experience, and those friendships make our journeys so much more meaningful.

Maybe you ate dinner in someone’s home and talked to them about everyday life in their country. Maybe you got drinks at a bar or took a day trip with someone you met in your hostel. Maybe you struck up a great conversation with someone on a train.

Eventually, though, everyone goes their separate ways. When that happens, it’s up to you to maintain your new friendships. And since human connection is one of the most crucial components of sustainable travel, it’s worth discussing a few ideas for keeping relationships strong across state lines and international borders.

Sustainable friendships: three women in a building in Paris.First things first: it’s important to remember that you can’t become lifelong friends with everyone you meet during your travels. That said, it’s definitely possible to keep in touch with the people who mean the most to you — the ones with whom you spent the most time, shared the most laughs, or created the best memories. After all, you probably already categorize the people in your life as “childhood friends,” “college friends,” and “work friends,” so why not add “friends from Europe, Asia, or South America” into the mix?

With that in mind, the most important thing is to exchange contact information with those people. Then, when you’re home again, make sure to reach out! Find out what your friends are up to and update them on your own life, or at a minimum, wish them a happy birthday every year. If possible, talk to them on the phone or over FaceTime, Skype, WhatsApp, or Facebook Messenger. You’ll quickly realize that seeing your friends’ faces and hearing their voices allows for deeper connections than messaging does (although the latter is better than losing contact).

Try to set aside specific times to talk. If you live in different time zones, you’ll probably need to catch up over the weekends, late at night, or early in the morning, but you’ll be amazed by how long you can talk with someone on the opposite side of the world.

If you run out of things to say about your own lives, you can recommend music, books, movies, TV shows, or podcasts that you think the other person might like. It’s an easy way to connect, and it can turn into one more (albeit small) interest that you and your friend have in common.

Sustainable friendships: two people in a restaurant in Paris.Also, remember that your communication doesn’t have to be digital. In today’s world, many of us forget about snail mail, but that makes it even more fun to send or receive something the old-fashioned way. Whether it’s a letter, postcard, care package, or something obscure that plays on an inside joke, put some thought into it and send it off. (And keep in mind that you don’t have to spend a lot of money to brighten someone’s day.)

If you’ve lost contact with a travel friend but you’d like to reconnect, you can always do that too. I lived in Ireland for a few months in 2016, and when I got back to the U.S., I began working on a project about the Emerald Isle. There was still a lot that I didn’t know, so I reached out to a few Irish friends and set up times to Skype. It had been a while since we’d talked, so once we finished going through my questions, we dove right into our own lives. The conversations were fun and lively, and it was a great way to catch up with the people I truly missed. But, of course, you don’t need an official reason to get back in touch — just reach out and see what happens.

As you keep up with your international friends, you’ll quickly realize something: you can only rehash a memory so many times — and, as Dr. Irene S. Levine once said, “A friendship can’t just exist on the past.” If you only discuss your shared travel experiences, you’ll both get bored, and it’ll feel like those memories are the only things you have in common. That’s why it’s so important to do more than just message someone. Real conversation gives new life to long-distance friendships.

Sustainable friendships: three women stand beneath the Arc de Triomphe in ParisIdeally, you’d be able to meet up with your friends regularly, but realistically, that’s probably not possible. What you can do, however, is make plans to occasionally see each other. Whether you return to the place where you met, invite your friends to visit you at home, or travel together in another part of the world, you’ll enjoy creating new memories and spending quality time with each other. It’ll make your friendships feel that much more meaningful and alive.

It takes work to keep long-distance friendships strong, and the quality of your relationship will only be as good as the effort that you both put into it. (Take it from someone who has the tendency to fall out of touch with old friends — I’ve seen the difference that a little effort can make.) If you spend the necessary time and energy, your reward will be a rich friendship, great memories, and the opportunity to learn more about another culture or way of life.

So, when people ask what you gained from your time in Italy or China or Peru, you can say “new friends” — the best takeaway of all.

Who have you met during your travels, and how have you kept those friendships strong? Let us know in the comments!