Charles is never happier than when he’s at the operating table. A heart surgeon with 20 years’ experience, he runs a coronary bypass clinic. The more difficult the operation, the greater the pressure to work fast, with no room for error whatsoever, the more he’s in his element. The adrenalin coursing through his veins makes him quick and happy in his work, his brain feels sharp, his movements accurate and fluid. He claims these are sensations he only ever feels in the operating theatre.

For Yolanda, it’s the moment just before the curtain goes up. Even though she’s been an actress for more than 20 years, her heart races, her throat tightens, her hands go clammy. But she knows that without this stage fright she couldn’t give a great performance. For other people, it may be public speaking, skiing down glaciers, hang-gliding, or even going into labour that focuses their attention and takes them to that physical and mental state of heightened sensory stimulation.

At these moments, on a purely physiological level, the body is in a state of intense stress: rapid heartbeat, adrenalin and cortisol flowing through the veins. But in the case of the surgeon, the actress stepping on stage, the top-level sportsman, even the woman about to give birth, this isn’t ‘negative stress’ in the sense that we normally understand it. We could call it ‘positive stress’, a powerful response from the body adapting to a challenging situation. What distinguishes positive stress from negative stress is psychological factors.

Without stress, we would not be fully stimulated. Our skills and reaction levels would be under-used, and we wouldn’t develop new ones. When a challenge outstrips our capacity to handle it (an exam we’ve failed to revise for, a flood, a terrorist attack), we experience mainly negative stress. But if we have the ability and the will to tackle something, the body’s response quickly calms down.

Overcoming challenges is invaluable for our personal growth, but it’s not easy. In order to transform a crushing failure into a personal challenge, certain things need to be in place. We need to have chosen to confront the crisis, we need the skills to tackle what is required of us, and we need to have the right kind of support during and after the experience – a good lawyer during a divorce, friends to reassure you that you’re still a good person… We now know that post-traumatic stress syndrome can result from the aftermath of an overwhelmingly stressful situation. We’re also now learning about the condition of post-traumatic wisdom – wisdom that is born of new perspectives, understanding and acceptance, which can be formed in the crucible of life’s many challenges.