"People who have never had a period of living with anxiety and panic don’t understand that the realness of you is an actual feeling that you can lose. People take it for granted. You don’t get up in the morning and think, as you spread peanut butter onto your toast, ‘Ah, good, my sense of self is still intact, and the world is still real, I can now get on with my day.’ It’s just there. Until it isn’t. Until you are in the cereal aisle, feeling inexplicable terror. When trying to express what a panic attack feels like it’s easy to talk about the obvious symptoms: the racing thoughts, the palpitations, the tightness of the chest, the breathlessness, the nausea, the tingling sensations inside your skull or your arms and legs. But there is another more complicated symptom I used to get. One which I have come to realise is at the heart of what my panic attacks have always been about. It is the one called, tellingly, derealisation. Within a feeling of derealisation, I still knew I was me. I just didn’t feel I was me. It is a feeling of disintegration. Like a sand sculpture crumbling away. And there is a paradox about this sensation. Because it feels like both an extreme intensity of self and a nothingness of self. A feeling of no return, as if you have suddenly lost something that you didn’t know you had to look after, and that the thing you had to look after was you."