I once interviewed Karl Pillemer, the Cornell sociologist and author of "30 Lessons for Living: Tired and True Advice from the Wisest Americans." He'd seen numerous studies showing that people in their 70s, 80s, and beyond were far happier than younger people.

He was intrigued: "I keep meeting older people — many of whom had lost loved ones, been through tremendous difficulties, and had serious health problems — but who nevertheless were deeply fulfilled and enjoying life. I found myself asking: 'What's that all about?'"

It occurred to him that maybe they see and understand things that younger people don't. But to Pillemer's surprise, no one had conducted a study on what practical advice older people had for the next generations.

That set him off a seven-year quest.

Their No. 1 lesson for a longer, happier life: Time is finite, don't spend it regretting things

"The older the respondent," Pillemer found, "the more likely [they were] to say that life passes by in what seems like an instant."

When elders say that life is short, they're not being pessimistic. They're trying to offer a perspective that they hope will inspire better decisions — ones that prioritize the things that really matter.

"I wish I knew this in my 30s instead of my 60s," one man told Pillemer, "I would have had so much more time to enjoy life."

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According to the older adults Pillemer interviewed, these are the most valuable things you can do with your time:

1. Say things now to people you care about — whether it's expressing gratitude, asking for forgiveness, or getting information.
2. Spend the maximum amount of time with your parents and children.
3. Savor daily pleasures instead of waiting for "big-ticket items" to make you happy.
4. Work in a job you love.
5. Choose your mate carefully; don't just rush in.

The list of things they believed weren't worth their time was just as revealing.

1. No one said that to be happy you should work as hard as you can to get money.
2. No one said it was important to be as wealthy as the people around you.
3. No one said you should choose your career based on its earning potential.
4. No one said they regretted not getting even with someone who slighted them.

And the biggest regret they had? Worrying about things that never happened: "Worrying wastes your life," one respondent said.

'Happiness is a choice, not a condition'

Pillemer described the people in his study as "the most credible experts we have on how to live happy and fulfilled lives during hard times."

At one point, he asked a participant to explain why she was so content. She thought about it and answered, "In my 89 years, I've learned that happiness is a choice, not a condition."

Pillemer noted that the elders he spoke to made a key distinction between the outside forces and events that happen to them, and their internal attitudes about happiness.

"Happiness is not a passive condition dependent on external events, nor is it the result of our personalities — just being born a happy person," he said. "Instead, happiness requires a conscious shift in outlook, in which one chooses — daily — optimism over pessimism, hope over despair."

The more we age, the more we come to see things the way that the Roman emperor Marcus Aurelius did: "When you are distressed by an external thing, it's not the thing itself that troubles you, but only your judgement of it. And you can wipe this out at a moment's notice."

Imagine that: all the choices that make up your career and personal life ultimately add up to an overall decision to be happy. You decide what to pursue in life and what's a priority for you. You decide how to best channel your time, energy, and resources.

Shane Parrish is the entrepreneur behind Farnam Street, host of The Knowledge Project Podcast, and New York Times bestselling author of "Clear Thinking: Turning Ordinary Moments into Extraordinary Results." He has been featured in major publications, including the New York Times, The Wall Street Journal, and Forbes. Follow him on X and LinkedIn.

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