Friendships are one of life’s greatest treasures. It is within deep friendships where we can feel comfortable to be our authentic selves. Friends celebrate the good times and carry us through the hard times. Friendships can bring joy and fulfillment and connection and belonging.

And friendships can be hard to build, and sometimes even harder to maintain. Here are three ingredients that can build and sustain lasting friendships.

1. Vulnerability

A friendship without vulnerability will always be superficial. And we all have superficial relationships – with acquaintances we see a few times a year, with friends-of-friends, co-workers, and extended family. We won’t have deep, meaningful connections with every person we meet. But when we want a relationship to extend beyond the superficial, vulnerability must be present.

Vulnerability simply means to be okay stepping outside of our comfort zone and accept the “emotional exposure”, as Brene Brown says. This means that we have to take small risks and put ourselves out there, even when we’re not sure how the other person will react.

Vulnerability in friendship might mean asking for help when you’re having a hard time. It might mean being honest about something that bothers you. It might mean sharing about a part of yourself you don’t tell everyone. When we are vulnerable with others, we invite others to be vulnerable with us.

2. Fun

An essential component of friendship is shared experience. New experiences are the fuel that keep a relationship moving along. Ever notice how so much of our time with old friends is looking back at memories together?

While deep connection and vulnerability and sharing are all important, so is lightness and fun. Most of us need a break from heavy things from time to time, and our relationships do, too. Whether it’s planning a fun outing, watching a favorite movie together for the 100^th time, having a game night or party, or making plans to visit each other (or meet somewhere in the middle), a fun shared experience can release tension, help you both relax, and create a new memory to look back on some day. Bonus points for something that meets your collective definition of fun – so while a dinner out might be great to catch up, a costume party, karaoke, axe throwing, crafting, a cooking class or a day trip might make an even bigger impact on your friendship.

3. Connection

Lastly, we can’t downplay the importance of connection. In the context of friendships, connection is first and foremost about just simply staying in touch. Many of us have those friendships that can go years without contact and pick back up right where we left off. But most friendships don’t work that way. Most friendships require some amount of regular contact before they dwindle and die. You don’t have to text all day every day, but a semi-regular check in can keep a friendship going.

But it’s more than just a simple “how are you?”. Connection also means checking in about the things that are really happening in each other’s lives. That might mean remembering to ask how things went after a friend’s parent had surgery or sending a “thinking of you” note on a friend’s first day at a new job. It might mean calling or texting when you see something that reminds you of your friend, an inside joke, a meaningful place, something pretty. Connection is the small heartbeat that keeps a friendship alive. It can often go unnoticed and unappreciated, but we are always aware when it stops.

With these three ingredients, we can make and sustain friendships – a truly essential component of our mental health.