My younger sister likes to remind me about the time I locked her in the closet.

Before you get too alarmed, let me clarify: we were eight and five years old. The closet had a flimsy screen door, which I think a good kick could have broken in half. It also didn’t have a lock, so ‘locking’ her in the closet consisted of me pushing on the door while she pulled on it and we both screamed for our mother. The entire ordeal probably lasted no more than thirty seconds, but to hear her tell it I may have well have been the Dursleys and she Harry Potter. You were so mean to me as a kid, she tells me. You’re always making up stories about me, I tell her.

As someone who studies conflict, I like my sister’s closet story a lot. It is such a personal reminder of how conflict is fuelled by stories, of how we give power to things through stories. The closet incident would have been meaningless if it hadn’t been a story — just as all the times that my sister bit me or I pinched her or she stole my dessert when we were kids. We have forgotten entirely about those incidents and they fade from our collective sisterly consciousness, meaningless moments drifting away unremembered.

But the closet incident has meaning because it’s a story. My sister reminds me (and my mom, and my grandma, and my friends, and her friends) because it has saliency for her and for us in the present. Sometimes she brings it up when I remind her of something mean she has done to me (“don’t pretend you’re so perfect, you locked me in a CLOSET!”). Sometimes she brings it up as a joke, fun memories of our childhood antics (“remember when you locked me in a closet? We were so crazy as kids.”). Sometimes she brings it up to remind us of the constant string of injustices she had to experience as a child, continuing onto the present injustice (usually about whether or not she can borrow the car) that she has experienced up until this moment (“This always happens to me! I was locked in a CLOSET and no one did ANYTHING.”).

It means whatever she decides it means, at the time.

There was an debate recently (or forever) about whether people in Northern Ireland need a shared narrative of the past or whether people in Northern Ireland need to respect each other’s differing narratives. The assumption seems to be: what’s the best way to draw a line in the sand?

The argument always reminds me of the slightly annoying tendency that couples in the honeymoon period often have, where they tell you “their versions” of how they started dating. You know what I mean—your friend says, “The whole time I was texting him because I thought he was so cute!” And then he says, “I just thought she wanted to study for our biology test together!”

Lines in the sand are so easily washed away, aren’t they? Couples constantly revisit the moments of their past together, even when they were both there for them. The act is part of a conscious process of coupling — you tell each other stories about the past, usually many times, in an effort to create a shared narrative about your past (or, at least, a shared humorous narrative about your divergent narratives). The process is dynamic, and the stories change as the relationship changes. Most couples don’t tell each other the truth of really embarrassing moments (usually involving how much they liked or didn’t like them) until they feel secure in the relationship. And these narratives can be part of conscious uncoupling — after a break up, stories that were sweet and cute can communicate bitterness; or, at least, something bittersweet.

Societies do this too. In the immediate aftermath of the Second World War, for instance, many Germans viewed the Nuremberg Trials of the Third Reich leaders favourably, as they felt betrayed by the Nazi government. This turned to bitterness and cynicism when the politics of the Cold War meant that Americans and their allies pardoned former Nazis that they had just condemned. It wasn’t until the 1960s, with the 1961-1962 Auschwitz trials in Frankfurt and the 1968 German Student Revolution that a real reckoning with the Holocaust and acceptance of the Nuremberg judgments really took place. With the way far-right politics in Europe is going, who knows what the meaning of the Nuremberg Trials will be in the next few decades.

The point is that we are constantly engaged in sharing and creating narratives about the past to build relationships in the present. The facts of what happened don’t change, but our stories about them do. The stories we tell ourselves are not based on some objective reality: they’re a choice.

This week saw the annual Twelfth of July celebrations. That is a statement which has meaning here. But if no one had told this uninformed American (me) anything, I would simply have thought a bunch of lads had decided to march down the street in slightly unusual outfits accompanied by varying degrees of talented musicians. It is only when someone tells me a story about the Twelfth that I begin to understand what it means, and that the event begins to have power.

In April, I did a series in the run up to the Good Friday Agreement anniversary about people who didn’t fit the usual Northern Irish ‘mould’ or stereotypes. What I was impressed by (in addition to their thoughtful commentary) was how much identity was a choice for these individuals. They didn’t talk about a moment in their lives when something external happened to change them — they talked about how they decided for themselves to change their story.

When I am feeling anxious and overwhelmed and frustrated about the state of the world (which is often these days), there is a mantra I like to remember: you cannot control how much love you get from the world, only how much love you give the world. I think the same is true of stories. You cannot control the stories other people tell, only the stories you tell yourself.

One day, my sister is going to stop telling the story about the closet — or she won’t, and she will go to her grave reminding me about it. It doesn’t matter how many times I have told her I’m sorry, or explained to her that it wasn’t really that bad, or said that I was only eight, or demanded she drop it and just forget about it. By the time we are 88 and 85, who knows how many times she will have told the closet story — but the meaning of the story will have changed over time, as our relationship changed. The significance of what the story means to her, what I mean to her, is a story only she can tell.

All I can control is the story I tell myself — whether the closet story means that I’m not a good sister; or that she will always secretly resent me; or that my sister is a mean-spirited and unforgiving person; or that there is perhaps within me some root of evil and cruelty because at eight years old I tried to put my little sister in a closet. On her deathbed she may curse me for the incident, and all of the other mean things which I will inadvertently or on purpose do to her in the intervening years—as well as all the nice things that she may or may not thank me for. But she’s my sister, and I’m stuck with her, and I love her even when she’s annoying me so much that I wish she was in a closet far, far away.

So, we keep writing our story.