Reassurance can actually exacerbate anxiety: when you reassure your friend that the worst-case scenario he fears probably won't occur, you inadvertently reinforce his belief that it would be catastrophic if it did. You are tightening the coil of his anxiety, not loosening it. All to often, the Stoics point out, things will not turn out for the best.

True security lies in the unrestrained embrace of insecurity - in the recognition that we never really stand on solid ground, and never can.

Confronting the worst-case scenario saps it of much of its anxiety-inducing power. Happiness reached via positive thinking can be fleeting and brittle, negative visualization generates a vastly more dependable calm.

Ask yourself whether you are happy', observed the philosopher John Stuart Mill, 'and you cease to be so.' At best, it would appear, happiness can only be glimpsed out of the corner of an eye, not stared at directly.

The routines of almost all famous writers, from Charles Darwin to John Grisham, similarly emphasise specific starting times, or number of hours worked, or words written. Such rituals provide a structure to work in, whether or not the feeling of motivation or inspiration happens to be present. They let people work alongside negative or positive emotions, instead of getting distracted by the effort of cultivating only positive ones. ‘Inspiration is for amateurs,’ the artist Chuck Close once memorably observed. ‘The rest of us just show up and get to work.

It is illuminating to note, here, how the daily rituals and working routines of prolific authors and artists - people who really do get a lot done - very rarely include techniques for 'getting motivated' or 'feeling inspired'. Quite the opposite: they tend to emphasise the mechanics of the working process, focusing not on generating the right mood, but on accomplishing certain physical actions, regardless of mood.

The real trick to producing great work isn't to find ways to eliminate the edgy, nervous feeling that you might be swimming out of your depth. Instead, it's to remember that everyone else is feeling it, too. We're all in deep water. Which is fine: it's by far the most exciting place to be.