Many of us will have a box stashed away in the bottom of a wardrobe or under a bed filled with memories from the past.  

Usually they’re sentimental things relating to a loved one or someone who’s died, but remarkably, about a third of people hold on to things from ex partners.  

Is this a form of self-flagellation, or is there a greater purpose for it?  

Brendan Kelly is Professor of Psychiatry at Trinity College Dublin and author of Resilience, which is out now