Friendships are not always are mutually exclusive. While we should be okay with that, we might actually feel uncomfortable that a very close friend has another close friend: “Because this person is so important to me, but they have someone else who is so important to them,” says Flannery. It can be helpful to remember that they are allowed to have other friends and that this does not threaten our friendship with them.

While research on the psychology of friendship is still developing, these relationships occupy much of our attention and energy in our daily lives. According to one Recent Pew Research Center survey61% of US adults who participated said that having close friends is extremely or very important for people to live a fulfilling life. One reason may be that people marry and have children later in life. In both the US and the UK, along with many other places in the world, the average age at which people get married has increased. In Britain, men and women now wait until they are over 30 years before marrying for the first time while in USA, the numbers are around the same age.

This means that for much of our lives, friends can provide the stability and support that was previously provided through marriage.

In romantic relationships, it’s not uncommon for couples to break up and then, after some reflection, get back together. Is this something we should also consider with our ex-friends – a reconciliation and a second try? Again, it depends on the nature of the friendship, says Flannery.

“I think there will be different times when that friendship heals versus other times when maybe it’s better to just let the breakup happen,” Flannery says. “And again, it might depend on: Are you relieved that the friendship is over? Did that friendship add positive benefits to your life? If you still feel like you really miss them, maybe they’re worth fixing.”

—

If you liked this story, sign up for The Essential List newsletter – a handpicked selection of must-have features, videos and news delivered to your inbox twice a week.

For more science, technology and health articles from the BBC, follow us on Facebook and X.