The last time I’d seen my ex had been six or eight months before, when I’d been single. After an excruciating run-in at a party, where I’d hoped to tell him I wanted to get back together and instead had to make small talk with his plus-one, I’d deleted his number and vowed to move on. I met my new boyfriend and fell happily into a new relationship. But when I saw my ex’s name on my phone, I couldn’t get involved in a WhatsApp conversation. It would have felt wrong because — although I was happy in my new relationship — even seeing his name gave me butterflies and shortened my breath. That didn’t mean I should be with him; it didn’t mean I wasn’t happy with my current partner. But I knew talking to my ex would feel, in short, too much like cheating.