Most of us are privileged enough to be able to think that we're in control of our own lives and responsible for our own destinies.
In one corner of this delusion, we think we get to construct our own health.
We go to the gym (or don't), we eat a lot of fresh fruit and vegetables (or not) and we give up smoking (please do), and we think that makes us healthy.
Not so fast.
Population effects overwhelm almost any personal decisions.
Since the late 1800s, life expectancy averaged among all Australians has increased by more than 30 years.
That's not because Banjo Patterson started eating organic and took up yoga; that's down to more sewers and better drugs. Society's choices, not the individual's.
And as we learned this year, giving up smoking won't save your lungs if the countryside starts its own 20-bushfire-a-day habit.
Mind you, all-Australian averages don't tell the story of Indigenous Australians.
The gap between Indigenous and non-Indigenous male life expectancy, for example, is up to 15 years, depending on which state or territory you're born in.
It takes a lot of workouts and kale to overcome that kind of population-level disadvantage.
Ride your bike, sure, it's good for everybody, but never forget that your most important organ is your vote.
I don't want to suggest that you shouldn't be looking after yourself. It's just that some of the important contributors to your health lie in the hands of other people.
We all want to be valued by other people, to be respected by other people, and when these needs are not met we tend to get sick.
It's not that surprising, then, that loneliness is getting to be one of our biggest health threats. Look, for instance, at my mother.
She was a tough old bugger, a survivor.
She'd lived through the war in London (her great delight was telling her grandkids Kess and Pete about how she and her friends would go out dancing while the air-raid sirens were going off), she'd had to deal with a difficult husband and she'd had three very independent and rebellious kids.
And then we grew up and didn't need her any more. She'd ring us up at work for chats, and ask us - beg us, some days - to drop over for a bite (or a drink - that sometimes worked).
We were all busy, and, shamefully, mum would take a lower priority.
She got lonelier. Towards the end, she got a little bit more bitter and twisted, which meant we visited less. We just put it down to old age, and being a tough - well, nasty - old bugger.
But it was loneliness.
We just watched as the bitterness grew. She went more often to the doctor for unconvincing illnesses. She probably had borderline depression.
But yes, she was tough, and that same tenacity finally saw her give up on us and find her own solution.
At the age of 78, she joined what I considered then to be a hokey little low-key elderly citizens' group.
Her world opened up like a Fabergé jewelled egg, and she had five years of joy.
With people just like her she talked, laughed, went on little trips, did little things.
It got to the stage that the only time she wanted to see us was when she felt like gloating about her new life and her amazing community group.
As the esteemed Professor Robert Putnam said ... a few decades ago ... "your chances of dying over the course of the next year are cut in half by joining one group, and cut to a quarter by joining two groups".
No longer lonely, no time for the doctor - a little community group had given her a place in the world (and yes, I know that doesn't let me off the hook as a neglectful son).
Do you want respect in your life, and human contact, and meaning?
Actually, that's not a question. You do, it's a scientific fact.
As the esteemed Professor Robert Putnam said, summing up the evidence a few decades ago in a journal article, "your chances of dying over the course of the next year are cut in half by joining one group, and cut to a quarter by joining two groups".
And that's something you, personally, yourself, can actually do.
You can join in and be part of something bigger.
There are 600,000 community groups in Australia, one at every corner of the country. Join a community group and live a good life for longer.