The quest for the elixir of life has led us down many paths. Everything from a diet of only fruit and nuts to indulging in a little bit of everything has been charged with the power to extend our lives.
But a new book by academic and clinician Dr Timothy Sharp suggests psychological health could be the key. Live happily and you will probably live longer, posits Dr Sharp, who describes the extra years many of us are now living as the gift of a "third age".
"Properly enjoyed, this phase of life need not be one of illness or decline but rather, for the vast majority of us, one of growth, wisdom, maturity and more," he says in the introduction to Live Happier, Live Longer.
The founder of the Happiness Institute and an Adjunct Professor in positive psychology at the University of Technology, Sydney, Dr Sharp has for many years been studying what makes us happy. But it was only when he was invited to talk about positive psychology at a financial planning conference a couple of years ago that he turned his attention to what happiness means for older people.
"A lot of the financial planners came up to me to chat and it became clear their goals in looking after their clients were similar to mine as a psychologist and life coach: advising people how to best live their lives," says Dr Sharp.
"Their strategies were mostly making sure people had enough money to look after themselves but they realised more than money was at stake."
Live Happier, Live Longer was not directly influenced by the debate about increasing the pension eligibility age to 70, but Dr Sharp says it is important to talk about the implications of working longer.
"What does work really mean now and what does retirement mean? The definitions are changing."
There are many positives about working later in life such as greater financial security and social connections, "which all help to lead a healthy life", says Dr Sharp.
"But I am not suggesting people should be forced to work longer because of financial necessity," he says, adding that many jobs would be too physically demanding for someone in their late 60s.
Live Happier, Live Longer examines scientific research that provides practical strategies to improve the quality and length of our lives.
Not surprisingly, exercise, diet and sleep are important, as are mental health, interpersonal relationships, a sense of belonging and purpose, and spirituality. The list is pretty much the same across the generations.
But Dr Sharp points out that some things come naturally to older people – such as worrying less about what others think of them, taking life at a more relaxed pace, feeling less angry. Others need to be worked at – mixing with younger people, having a strong purpose in life.
"Having a purpose in life is a core construct for leading a meaningful life rather than just a pleasurable life," he says. "But it becomes more important as you get older. It is about giving back to your children, your grandchildren, or mentoring younger people, sharing your knowledge and experience. When you are lying on your death bed you will not be wishing you had spent an extra hour at the office.
"One of my hopes with this book is that it will bust the myths about older people and that we start valuing and cherishing them, and bring back some of the respect we had for them in the past."