What’s “the most dangerous poison of life” — the greatest source of unhappiness?

You might think it’s hatred, and that would be a sensible choice.

But according to American Founder Thomas Jefferson, it’s boredom.

For an intelligent person, being alive means more than just having a heartbeat. It means to be doing something, going somewhere, pursuing goals that matter.

If you don’t have those, then you’re not fully alive: you’re just taking up space. Boredom is poison. Worthwhile activity is the antidote.

That’s what Jefferson told his daughter Martha in a 1787 letter from Paris. He advised:

“A mind always employed is always happy. This is the true secret, the grand recipe for felicity. The idle are the only wretched. In a world which furnishes so many useful employments, it is our own fault if we ever [get bored].”

You should always have at least one major purpose in life, an important goal toward which you are working.

If you achieve a goal, then feel free to take a celebratory vacation. But don’t stay on vacation too long.

Just as your muscles need rest after exercise but weaken if they rest too long, so you, your mind, and your character need occasional rest but weaken if you rest too long.

One reason that retired people sometimes age rapidly, get sick, and die before their time is that they don’t see the point of living anymore. They’ve lost their sense of purpose. “What am I doing here?” they ask themselves, and they have no good answer.

Make sure that you always have an answer. Always have a purpose.

Check out my book Why Sane People Believe Crazy Things: How Belief Can Help or Hurt Social Peace. Kirkus Reviews called it an “impressively nuanced analysis.”