It seems so irrational – why be jealous of what was history even before you met? ‘The mind does not always make distinctions between the past, present and future,’ explains therapist and relationship coach Marilyn Devonish, from coaching and therapy service Trance Formations. ‘That’s why your partner’s past relationships can feel very much part of your present.’

That explains why a recent jokey reference my husband made to his teenage love struck a blow. My mind knows their paths haven’t crossed for more than 20 years, and that she’s never posed a threat to our relationship, but the mention of her name made it feel as though she was a real and present danger.

How to handle retroactive jealousy:

1. Resist seeking reassurance

It’s tempting to look to your partner for comfort when consumed with jealous feelings, but that rarely helps. ‘No amount of reassurance can fill that hole, so avoid getting trapped in that destructive cycle and instead focus on the underlying insecurities,’ advises Devonish. Remind yourself of your strengths – what is fabulous about you?

2. Use social media with caution

Most of us have looked up a partner’s ex online. ‘But when that turns from a quick glance out of genuine curiosity to constant obsessive checking, it’s time to think about breaking from social media for a while,’ advises relationship expert Caroline Brealey from dating agency Mutual Attraction. Make a decision not to indulge in behaviour that will be unhelpful to your relationship.

3. Agree ground rules

Psychotherapist Richard Reid of Pinnacle Plus recommends agreeing boundaries with your partner so you both know where you stand. ‘Don’t restrict your partner’s freedom, but it’s reasonable to expect to have some say in the manner of the contact your partner has with their exes,’ he says. ‘Agree the ground rules together – no flirting or private messaging.’

Photograph: Jacob Pritchard/Gallery Stock

More inspiration:

Read How to spring clean your relationships by Sarah Abell on LifeLabs