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

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.

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.

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.

Through positive thinking and related approaches, we seek the safety and solid ground of certainty, of knowing how the future will turn out, of a time in the future when we'll be ceaselessly happy and never have to fear negative emotions again. But in chasing all that, we close down the very faculties that permit the happiness we crave.

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.

Uncertainty is where things happen. It is where the opportunities - for success, for happiness, for really living - are waiting.