And in the case of retirees, it may come down to one particular choice they make with their money.
Wes Moss, the chief investment strategist at Capital Investment Advisors and host of "Money Matters," interviewed over 1,300 retirees in 46 states.
He details the findings of his survey in his book, "You Can Retire Sooner Than You Think: The 5 Money Secrets Of Happy Retirees," where he writes about the qualities and trends he observed among the happiest retirees, from how they think to what they do every day.
He even examined what they drive.
Among all of those factors, there's one pattern that Moss highlights: Happy retirees live smack in the middle of their available resources.
"When it comes to home values, vacations, restaurants, cars, and shopping, happy retirees have found the sweet spot in the middle," Moss writes. "Nothing low-rent, but not high-end either. They're not spending lavishly - but they're also not depriving themselves. They've struck a balance that's right for them."
Research has found that it's not how much money you spend, but the way you choose to spend it, that most affects your happiness levels. Retirees who aren't struggling under artificially strict budgets, or expanding their spending to absorb every single dollar available, are presumably prioritizing the things that mean the most to them, and cutting back on spending where their dollars mean the least - an approach that could benefit any of us.