Long ago, I had an interview in New York with a well-known advertising agency. In the last of a round of interviews, the head of human resources used a phrase that I've heard with increasing frequency over the intervening years. She said: "Malcolm," (for that is I), "we try to make sure that we employ more Radiators than Drains."

The metaphor probably speaks for itself, but for the avoidance of doubt, Radiators are incorrigible optimists who warm others with their positive thinking, while Drains suck the life out of their colleagues with their negativity. If you Google 'Are you a radiator or a drain?', you'll find Oprah Winfrey quoted as saying "l wish I'd known how to distinguish Radiators from Drains" as one of her life lessons. There's no mistaking the value judgement lurking behind this categorisation. Radiators are clearly to be preferred, courted, and emulated, while Drains must be avoided, shunned, and should never be sought out as role models.

This got me thinking about how positive thinking as espoused and exemplified by Radiators is always celebrated as the best way to live long and prosper. As an example, admittedly extreme, of the grip that such positivity has on our culture, consider the success of the book, film and now website called 'The Secret'. On The Secret's website, its creator Rhonda Byrne makes the surprising claim that we can change life outcomes with positive thinking: "Decide right now that you're going to feel good. Intend that you're going to feel good today and tomorrow. Visualize yourself feeling good. And whenever you think of it, remind yourself to feel good now. That's it – life turned around!"

Now any sensible person will of course reject all this as quackery, but aren't we guilty of perpetuating just the same point of view when we say, or even just think, that people should 'always look on the bright side', that it's best to 'smile because then the world smiles with you', and even when we wish people to 'have a nice day'?

Unsurprisingly, this mandatory optimism exerts its influence on the world of work, too. When we praise Radiators and denigrate Drains, for example. When marketing briefs are written that are way too positive, bordering on 'wishful', about the desirability of a new product and overoptimistic about growth. Or, when agency teams blithely hope that the marketing team have understood what the CEO wants – which is important because the latter is too busy to meet before the pitch, but will invariably turn up on the day itself.

The really positive news is that there is an alternative to all this positivity, which I call the positive power of negative thinking. Adopting the positive power of negative thinking requires, first of all, setting expectations at a much lower level than is usual these days. As the psychologist Barry Schwartz puts it, "The secret to happiness is low expectations. When your glass is permanently half-empty, you can only ever have pleasant surprises." I look at our younger team members and wonder whether their restlessness to get ahead is admirable ambition or a distracting dissatisfaction brought on by expectations set way too high. Adjusting your mindset to the positive power of negative thinking means never working on a project, or even going to a meeting, thinking that everything will turn out alright. In fact, if you start thinking in this positively negative way, everything will be more likely to turn out well because you will have left no stone unturned in your preparation.

In my experience, the great thing about building teams around those who live by the positive power of negative thinking (aka Drains) is that they never stop trying and they never stop worrying about whether what .they are doing is the best they can do. These teams have the vigilant watchfulness that the American academic Barbara Ehrenreich points out was hardwired into our prehistoric ancestors so that they were permanently on guard, expecting the worst-case scenario of a T. Rex in the long grass. In her book Smile or Die: How Positive Thinking Fooled America and the World, Ehrenreich argues that being too optimistic may actually make illnesses worse, cause us to waste time and money improving ourselves when the real impediments to happiness lie outside our control, and even persuade bankers that they've got it all worked out. And we know where that got them and us.

I say, let's stop seeing negativity as a dark force. Instead, let's start regarding it as a realistic philosophy, making a positive contribution to work and the workplace. After all, Drains very often work much better than Radiators.