I think a big part of it is that many adults don’t give themselves many opportunities to make new friends. For many adults, the daily routine is: go to work, go home, repeat. If they do something out of the house, it’s usually something just with their family or partner, or with established friends. Contrast that to kids. While there are some kids that just go to school and come home, most kids are involved in at least a few extracurriculars—maybe they’re part of a sports team, or they’re in the choir, or they tried out for the school play. Each of these things gives them an opportunity to meet new people, and form new friendships. Even if they’re not involved in any extracurricular things, they still have more opportunities to make friends than the average adult, because every new class is a chance to meet a new group of people.

So the first thing I ask a social skills coaching client that wants to make more friends is “Well, what do you do with your free time?” If they don’t spend much time in contexts where it’s easy to meet new friends, I try to encourage them to start going to a meetup group or a volunteer group or something similar once or twice a week. In many cases, this has a huge impact on their ability to make new friends.

But I don’t think this is the whole story. After all, many people spend a lot of time trying to make friends, and still end up feeling alone.

And so I think the second piece of why it’s so much harder to make friends when you’re older is because as adults, we’ve learned to hold back our real selves from each other. When I was a kid, I would tell my friends my secrets. I would cry in front of my friends if I was feeling sad or upset. I wasn’t afraid to call someone my “best friend” and make it clear how much they meant to me.

But as I grew older, I learned to put up walls. I learned that if I was my real self, people would sometimes reject me. I learned that if I told someone a secret, they might tell someone else (even if they pinky-swore otherwise.) I learned that if I presented a happy-go-lucky, filtered version of myself, then I could avoid a lot of social rejection and a lot of awkwardness. And it’s really easy to take that version of myself to parties and social events and have a fun time, and then go home feeling really lonely because I never let anyone see the real me.

I mean, don’t get me wrong. You need the ability to put up walls when necessary. You don’t want to tell your deepest secrets to someone you just met. You don’t want to burst out crying when your boss gives you some harsh feedback. Part of being an adult is learning how to have those walls. But even the strongest castle walls had a gate that allies could come through—otherwise everyone in the castle would starve. And the walls around your real self were designed with gates that you could open when a safe person approached.

It’s just that many adults have forgotten how to work those gates. We either keep them closed all the time, and never really open up to those around us, or we open them right away, and risk getting hurt again and again by people who don’t deserve our trust. And I think this is why a lot of us adults struggle with making friends.

The number one thing that I tell people who are trying to make more friends is to be a real friend to someone else. Show them that you’re a safe person to open up to; show them that you are genuinely interested in who they are, and that you’re not going to reject or betray them. Let them open their gates slowly, inch by inch (don’t rush them), and open your gate in return. If you do that, no matter how old you are, I think you will find that it’s not so hard to make new friends after all.