This week I encountered The Fear. He was on a holiday park in North Devon, of all places, roaming between the static caravans that sit on a hillside overlooking the bay. I’m pretty sure most parents meet him at some point, but this week was my turn.

I’ve been anxious about Izzie before, concerned about her safety, worried about the future, but it’s always been small scale, fantasy-land fear, the kind you get before the dentist or a particularly unpleasant meeting – you’d rather avoid it, but you know that if you have to face it, you’ll get through the discomfort because it’s not really actually all that bad. The Fear is another matter entirely.

It crept up on me unannounced. Everything was fine – a bright, crisp morning, fluffy white clouds scudding across an azure sky, the ocean stretching out below us towards the horizon. Lizzie was walking down the hill holding Izzie’s hand and while I locked up the caravan, my little girl looked over her shoulder at me, the breeze tousling her hair. Her face was a picture of innocent joy, her toothy smile so infectious as she waved at her daddy that in that moment I knew what it was to be loved and what true happiness felt like.

And an instant later I was struck by The Fear – the all-pervading, nausea-inducing, gut-wrenching, knee-weakening presentiment that I would lose her.

The closest I’ve come to this feeling before is when Izzie was around three months old. I went into her room in the middle of the night to check on her and she was so still and quiet I thought she was dead. My first thought – nay, instinct – was to travel to wherever she had gone, because she needed me and I couldn’t bear the thought of not being there for her. Short story even shorter, she wasn’t dead, she was just asleep – but the incident cleared up any lingering doubts about whether I truly believed in the hereafter.

The Fear wasn’t like this at all. It didn’t come from anything scary but from something joyous. It was as though upon reaching the heights of happiness, my body reacted and rebelled, viscerally and violently. Out of the clear blue sky I was filled with the most terrible and heartbreaking dread.

I’m not just talking about death, though that’s a given – cancer, meningitis, kidnap, murder, an accident, The Fear showed me it all – I’m talking as much about change. If I could have frozen that moment she waved at me with innocent joy, I would have done, because right now Izzie adores me – I’m the smartest, coolest, funniest, most-lovable chunk of a man she knows. But all that will change, and quickly too. My days as my daughter’s faultless hero are well and truly numbered.

I spent all that day with The Fear. Maybe, I thought, it’s here because I was talking to somebody about Seneca a few days ago, and his belief that your mind is the only thing you can rely on as everything else you can lose – friends, family, status, job, home, health, hair, all of it. Or maybe, I thought, I’m preoccupied with losing Izzie because police believe they might be days away from locating the body of Ben Needham, a British 21-month-old who went missing 25 years ago in Kos. Or perhaps it’s because I had the unfortunate experience of overhearing a fourteen-year-old girl and her mother screaming life-affirming statements at one another like, ‘I’ve effing had it with you,’ ‘you effing well ruin everything,’ and, ‘I wish you were effing dead!’

But that’s not it at all. If it was, The Fear would be with me all the time. No, it’s because in that moment of perfect happiness I realised my unbridled love for another person – and simultaneously my utter and total vulnerability. Izzie has me, heart and soul, and if anything happens to her, I would be destroyed. The Fear was a safety mechanism, a reality check, because I was walking too close to contentment, and believed my happiness to be immortal. Keep away from the sun, Icarus, or you’ll fall into the sea.

And that is the dilemma of parenting. You give yourself and hold nothing back, but in so doing you risk everything. Your fate is tied to that fragile, fickle bundle of cells you call your child. And the price for your joy is The Fear, cropping up when you least expect him, reminding you you’re dancing with a moonbeam that can never be contained.

But in the meantime, long live this moment.