Spending time worrying about things that are never likely to happen is wasting energy and therefore making you less happy, a philosopher claims.
And for chronic worriers, the energy spent on fretting about what tomorrow may bring can lead to downright grumpiness.
Shane Mulhall, head of the School of Philosophy and Economic Science in Dublin, is in town to offer some tips to Kiwis who find it hard not to worry.
The lecture, Energy and How to Manage It, has been delivered in Auckland and will be repeated in Wellington this week.
Speaking about his ideas, and with a big smile on his face, Mr Mulhall is the first to admit his prejudice.
"I would say that the Irish are the most naturally happy people in the world," he laughs.
Asked if Kiwis are a happy bunch of people, he hesitates.
"If I was to describe New Zealanders, I would say strong, steady, reliable, consistent - if they say they will do something, they will."
Mr Mulhall was invited here by the School of Philosophy in Auckland, which has been offering lectures in practical philosophy for 52 years.
The whole concept of the lectures, he says, is about getting across the need to know how to take care of oneself, physically, but more importantly, emotionally. "The idea of the talk is to point out how we use our energy and how we waste it - and then looking at ways not to use it and not to waste it.
"If people get depleted of energy, it's very easy to become depressed or miserable, downcast or pessimistic.
"Whereas people who can utilise their energy properly, then they tend to live efficient lives. They tend to be happier ... and even more intelligent.
"Think about it - when you're tired you can make very stupid mistakes ... You can become grumpy and irritable.
"We waste energy in lots of ways, like worrying about things that are never going to happen, but still worrying about them.
"It's like New Zealanders and rugby. Can you imagine if the All Blacks had lost the World Cup? The whole country would be in mourning."
Last week, Mr Mulhall met students studying philosophy at the University of Auckland.
He said people should be reminded to live in the moment and not get worked up over little things that weren't actually worth the worry.
Worriers, he said, were "people getting angry over absolutely nothing. They drop their keys into a puddle or their shoelace breaks and they think the world is coming to an end."
Mr Mulhall gave his first lecture on Saturday in Mt Eden before travelling south to Wellington for his talk there on Thursday.