Here's how to stay friends with your ex

Couples therapist Esther Perel , author of "Mating in Captivity" and "The State of Affairs: Rethinking Infidelity" and the host of the Audible original series "Where Should We Begin?," reveals why people can be friends with an ex and how you can maintain that friendship and your current relationship.

Esther Perel: In the past, when a relationship ended, that was it. Most of the time you had no way of finding the person anymore. You had moved. They had moved. Who knew?

Today we have the capacity to actually go and find out whatever happened to that person. And what's their life like. And what would my life maybe have been like if I had stayed with that person. I get to actually have a glimpse into the stories that I didn't choose to live.

It's all a matter of trust. Can people stay friends with people they once had a romantic relationship with? Absolutely. Can people do so in a way that is not threatening to their relationship and integrate their partner into it even - even if less than they themselves are? Of course that too.

The question is a question of trust, of openness, and of clear boundaries. It makes sense that some people would be able to develop a beautiful friendship with someone with whom they once shared a more intimate relationship. It is a person they often trust, it is a person they know, and it is a person that they've had a story with and a history with.

Today, most of us will come to our committed relationships after years of other relationships and sometimes other sexual nomadism. It used to be that we married and that we had sex for the first time. Today we marry and we stop having sex with others. Exclusivity - emotional or physical exclusivity - means something very different when you have had other partners.

The degree to which we learn to integrate partners, friends from different times in our life in the context of the current relationship that we are in, is a new challenge for many couples for which there are often no prewritten scripts. And so each couple needs to negotiate that. What is ours and what is mine. What do we share and what remains ours individually. The question for every couple today, of togetherness and separateness, is a must-have conversation for every couple, with individual answers often for every couple.