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One of the strangest aspects of adulthood—one that no one seems to warn you about when you're younger—is that it can be hard to make friends as a grown up. Sure, you may really like the office manager at your work, even grabbing lunch together on occasion, but if you change jobs, will you still see each other? Same goes for those friendly parents from play group. You may host playdates for the toddler years and then one day your children realize they have nothing in common and the families drift apart.

While you may still be BFFs with your high school friends and college buddies, frequently it feels like adult friendships have a built-in expiration date. However, that doesn't have to be the case.

Here are a few tips for how to make lasting friendships as an adult:

Don't Discount Casual Acquaintances

Making small talk while waiting in line at the grocery store or chatting with the person sitting next to you at the DMV can plant the seeds of a friendship. A 2014 study showed that simple friendliness—even just exchanging pleasantries with the folks around you—can actually make people happier.

Don't Seek Out "A Twin"

One of the mistakes that adults make when looking for friends is looking for someone who is just like them, Shasta Nelson, the author of Friendships Don't Just Happen!, told Real Simple. Just because someone is single, while you're happily married, or is an avid runner while you are an experienced couch potato, doesn't mean that you have nothing in common. If you both love beach clean ups, Zumba, or reading, that can be enough to build a lasting friendship. Keep an open mind and find someone who shares your sense of humor, makes you feel happy, and may even challenge you to try something new.

Be A Good Listener

Good listeners make for good friends, because people like being heard and having someone pay attention to them. There's some science to back this up, too. A 2016 study found that increasing your likability can be as easy as listening to someone and simply asking them to tell you more. In fact, "Tell Me More" was the name of their study. Good listening doesn't just mean being present or nodding your head occasionally, but actually following the conversation, asking questions, and delivering specific, manageable advice. And as a modern etiquette reminder—part of being a good listener also means not looking at your phone during conversations.

WATCH: Study Shows The Best Kinds of Friends Are The "Mean" Ones

Re-Connect with Old Friends

Remember that old song about making new friends, but keeping the old? There's some scientific truth to it. A study in Organization Science revealed that reconnecting with old friends is particularly rewarding for people. The authors wrote, "Reconnected friends can quickly recapture much of the trust they previously built, while offering each other a dash of novelty drawn from whatever they've been up to in the meantime." Social media makes it easy to reconnect, but if you dare, get off Facebook and meet up in real life for a good old-fashioned catch up.

Open Up

While it can be hard or even scary to share intimate details with new people, sharing something personal can make others feel trusted and appreciative and can build relationships. This isn't an excuse to share TMI about your upcoming bunion surgery, but perhaps opening up about your dislike of the office coffee, your child's inability to sell a single box of Girl Scout cookies, or some funny family drama. It's what one psychology professor has dubbed the Goldilocks principle of sharing not too much and not too little, but just the right amount of personal details to help grow the friendship. There are good reasons to give it a try, too. As The Atlantic notes, citing this 1994 study, there are two good reasons to open up— disclosing personal information makes people seem more likable, and it also makes us like the people we have opened up to.

Prioritize Friendship

Once you make plans with someone, follow through. Don't be the person who is always saying, ‘oh we should get together sometime!' Pick a date, put it on the calendar, and don't cancel except in emergencies. Annie Wright, a licensed psychotherapist, told NBC News, that even if you have a packed schedule, prioritizing friendship is a key part of making new friends, as it proves that you value the other person's time and their friendship.

Finally, try not to worry about it so much

Nelson, the author of Friendships Don't Just Happen!, told Real Simple that we replace our friends every seven years or so for most of our lives. Basically, this friendship carousel is a normal part of life.