Agi Heale's first panic attack came out of the blue. She was by her desk in the middle of the day, at the financial services recruitment company in London where she then worked. "There was nothing particularly significant to trigger it," says Heale, now 34. "I was working as normal and then I was just blindsided."
For the next several minutes, Heale experienced a set of physical symptoms: "My heart rate went through the roof," she says, "my palms were sweating, my stomach somersaulting, and I couldn't think. I sat there, stubbornly trying to fix myself."
When it became apparent that whatever was happening was beyond her control, Heale just got up and left, calling her fiancé on the way to warn him that she was experiencing something strange.
"By the time I reached home, I felt OK again," she says. "But I couldn't admit even to myself that what had just happened was something to do with my mental health."
Looking back, Heale says she can see that there were escalating signs of anxiety setting in before her first experience. But like many of us, she was unaware of what a panic attack looked or felt like, let alone considering herself to be at risk.
In fact, according to the Mental Health Foundation, 13.2 per cent of us experience a panic attack at some point in our lives, with typical symptoms similar to Heale's: an experience of sudden and intense fear, often accompanied by physical symptoms such as a racing heart, rapid breathing or upset stomach.
The physical effects of panic are thought to have contributed to young British tennis hopeful Emma Raducanu's retirement from her Wimbledon fourth round match last week. Raducanu, 18, has said she "started to breathe heavily and felt dizzy".
Emma Raducanu leaves court at Wimbledon after breathing difficulties. Photo / Getty Images
She told the BBC: "I found it very difficult to regulate my breathing," adding: "I don't know what caused it, I think it was a combination of everything that has gone on behind the scenes and the accumulation of the excitement and the buzz."
Panic attacks are caused by the body's fight or flight response to the feelings of anxiety and fear. The body releases adrenalin, which makes the heart beat faster, increases blood flow around the body, and stimulates the body to make glucose for energy. But sometimes that can make us feel dizzy or even hyperalert, especially if the body does not have to do anything – such as run.
Triggers for panic attacks will vary for everyone, but stressful life events are often to blame. The stress of the pandemic has led to increasing rates of depression and anxiety, suggesting more of us will have experienced these moments of high adrenaline output, too.
After that first episode, Heale, who lives in Singapore with her husband, who works in finance, and their two young children, continued to experience panic attacks – and discovered she was not alone.
"I found that the stress and anxiety I experienced was remarkably common among people like me in their 20s and 30s," she says.
"At the age we should have been enjoying ourselves most, my cohort were panicking about not achieving enough. In my head, I started thinking of us as Generation Panic."
That name is now on the cover of a book, written by Heale, which is designed to help anyone of any age through panic attacks and anxiety, via numerous different techniques and tips.
The book is designed not just to be read once as an explanation of what you might be feeling but also as a handbook to be referred to whenever the reader experiences that first twinge of panic.
"There are 47 chapters," says Heale, "and all are full of tips and strategies you can use to get yourself back into balance and stay there."
Examples include celebrating the mundane, changing your landscape and a neat idea where you put yourself in the shoes of others and ask what wisdom they could offer you. These "others" might include your 3-year-old self, your 80-year-old self, a politician you respect and even your favourite singer.
For Heale, the chapters represent 47 documents she wrote for herself on her PC once she had decided her panic attacks could be brought under control.
"At the time I had my first attack," she explains, "I was aware of being stretched. Our wedding was due two months later and I assumed that was the issue. But afterwards, I still kept feeling anxious.
"I didn't really think to go to my GP but my mother mentioned that she thought I was having panic attacks."
She started researching the issue and realised she needed to step back from working so hard and start developing some self-care techniques.
Agi Heale: 'I really felt that having made so many discoveries, I had a duty to share them with others'. Photo / Supplied
She cut out alcohol – aware that it could leave her irritable and sensitive, which made anxiety more likely, and reduced her social diary, slowing down her pace of life. Heale began seeing a life coach to help her improve her work life balance.
"Then I started writing down everything that I learnt in a collection of files, which was to become the book. I really felt that having made so many discoveries, I had a duty to share them with others."
Since the book was published, she has heard from people of all ages who say the techniques have helped them, from a 94-year-old who wrote to say she loved it, to a mother who was using it with her teenage daughter.
"What works for one won't necessarily work for another. My advice is to read through and find what works for you; it's a companion for anyone struggling with the weight and demand of our fast-paced life."
Heale has her own favourites for when she starts to feel under pressure. "Deep belly breathing is the one thing I go to every time. Countless pieces of research have shown it to help clarity of thought and that it slows the heart rate.
"Another favourite is to imagine an undercurrent of electricity coursing through your body. Then you stand up and physically flick it off your body, rid yourself of the energy."
Heale is a big fan of the support network too: "Find others you can talk to about how you feel. You aren't alone with anxiety. Just by acknowledging you have a problem you are starting to get better. We are all so determined to come across as strong and excelling at everything but that just isn't realistic."
Heale moved to Singapore three years ago with her husband and their first child, who was five months old at the time – "That was stressful," she says, with understatement. But all the research then came into its own: "I had enough tools in my toolkit to pick and mix what I needed to do to stay calm."
1. Form fists under the table and squeeze for 5-10 seconds, then release. Stretch out your fingers fully. 2. Tense your legs. Uncross them, put your feet flat on the floor and then squeeze them. Curl your toes and hold for five seconds. 3. Release your jaw and wiggle it around 4. Go for a light stroll, slowing things down and taking in what is around you 5. Breathe deeply from your belly, not the top of your chest, taking your time when inhaling and exhaling.
Generation Panic by Agi Heale (RRP £11.99). Buy now for $21.82 at books.telegraph.co.uk