If a new study is to be believed - despite the fact that it seems to contradict almost every previous study - the more pessimistic one is about life in general, the longer one is destined to live.
This appears to throw almost everything we've heard about optimism and happiness into the mental rubbish bin.
We're supposedly healthier and heartier because as New Zealanders, we're now ranked eighth in the United Nations World Happiness Index.
In every slideshow presentation in the past 10 years, someone has slipped in a glowing reference to Bhutan, the country that turned from measuring Gross Domestic Product to totting up Gross National Happiness. (Notably, fans of this approach don't themselves feel inclined to leave their own flat-screen TVs, high-tech gadgets and free-flowing tap water to relocate to the tiny, impoverished kingdom).
One of the world's most popular self-help books, The Secret, proposes that relentlessly positive thoughts alone will attract a better life (on the flip-side, all this positivity may drive away all your friends).
The recent trend to "slow living" - less processed food, fewer chattels - may be trying to impart a different type of happiness, but its thrust is much the same; it's still glass half full (of milk from happy, organic cows) kind of stuff.
Now we learn the precise opposite is true. Researchers at the University of Erlangen-Nuremberg in Germany, who studied 40,000 households over a decade, say being pessimistic about life may extend yours by some 10 per cent beyond that of your overly cheerful chums.
Notwithstanding the fact that genuine happiness for the purposes of science is more a feeling of contentedness than constant ecstasy, the study clearly shows that being too content can be your downfall. Overestimated life satisfaction is linked to a higher chance of an early death or disability, even if you are otherwise healthy and wealthy.
Pessimists, or realists, come out better, and it is older people feeling the twinges of decay who are most realistic about their prospects. In the German study, 43 per cent of the aged gloomsters underestimated their future life satisfaction, 25 per cent predicted it accurately, while 32 per cent of them overestimated how happy they would be.
The pessimist, the study found, expects bad things to happen and moves to avert risk and pre-empt medical disaster wherever possible, living longer. Such people have a mindset best summed up thus: expect very little and you'll never be disappointed.
We all know people who live their lives with this philosophy front and centre. They tend to be tiresome in their ceaseless negativity and certainly out of sync with the modern drive to the upbeat, chillaxed vibe we're all anxious to adopt.
They'll claim to have one foot in the grave for decades at a stretch, giving everyone the idea they long ago gave up on living. These are precisely the kind of people who live longer, the study says, probably pleasantly surprised they've done so (while pessimistic about their prospects of surviving another day).
So, next time someone tells you to think happy thoughts or treasure your half-full glass, you not only have the right to be annoyed by their spouting of meaningless aphorisms; you can also tell them you are looking to prolong your life by adopting a suitably dark outlook.
Then laugh maliciously, as they slowly back away.