Back in the late 1980s, Dana Carvey of Saturday Night Live used to do a funny impression of US President George H.W. Bush, in which the character would justify his own supposed timidity by muttering "wouldn't be prudent" to himself about every small risk. The impression neatly captured the contemporary notion of prudence: faintheartedness, caution and a general bias against action.

So perhaps it seems odd that this is my advice for young people heading out of school and into the world: Be prudent. Yes, it sounds boring, but it may turn out to be a more radical suggestion than what most graduates hear. I thought prudence was not my cup of tea. When I quit college to go on the road as a musician, I was being imprudent. When I quit music to go back to school in my 30s, it was imprudent. When I left a tenured professorship for an unsecure job? You guessed it - imprudent.

Then I had an epiphany. When I read German philosopher Josef Pieper's The Four Cardinal Virtues, I was shocked to learn that I didn't hate prudence; what I hated was its current - and incorrect - definition. The connotation of prudence as caution, or aversion to risk, is a modern invention. "Prudence" comes from the Latin "prudentia", meaning sagacity or expertise. The earliest English uses from the 14th century had little to do with fearfulness or habitual reluctance. Rather, it signified righteous decision making rooted in acuity and practical wisdom.

We have refashioned prudence into an excuse for cowardice, to avoid what Pieper called "the embarrassing situation of having to be brave". The correct definition, he argued, is the willingness to do the right thing, even if that involves fear and risk.

In other words, to be rash is only one breach of true prudence. It is also a breach to be timid. So which offence is more common today?

A study by University of Chicago economist Steven Levitt helps answer this question. He started with the premise that people who agonise over important choices may systematically make wrong decisions, defaulting to either "yes" or "no" with too much regularity.

To investigate, Professor Levitt found several thousand people in the throes of a difficult decision, weighing choices like job offers and marriage proposals, who volunteered to let him make the decision for them - with the flip of a coin. Heads meant to decide in the affirmative; tails meant to decline.

When given heads, he found people were much more likely to take the decision affirmatively than they would be if left to their devices, so the experiment was effective. But the really interesting result concerned the participants' happiness. In follow-up interviews six months later, Prof Levitt found that the average "heads" person was significantly happier than the average "tails" person.

Here's what all this means: Our sin tends to be timidity, not rashness. On average, we say "no" too much when faced with an opportunity or dilemma.

Data collected by the National Opinion Research Centre shows people under age 30 today are a third less willing than under-30s in 1996 to relocate for their careers. And as economist Tyler Cowen observes in his new book, The Complacent Class, the fraction of people in this age group who own their businesses has plummeted by about 65 per cent since the 1980s.

Yes, economic changes have contributed to both trends. But another culprit is a diminishing frontier spirit and an increasing paranoia about taking big leaps.

Family formation looks to be another victim of this imprudent hesitation. The Census Bureau says that while only a quarter of 24- to 29-year-olds were unmarried in the 1980s, almost half of that age group is unmarried today. Last August, the Centres for Disease Control and Prevention announced that the United States fertility rate had fallen to its lowest point since they began calculating it in 1909.

My chequered past, it turns out, may not be a litany of imprudent decisions. True prudence means eschewing safety and familiarity in favour of entrepreneurial living. It requires clear eyes, a courageous heart and an adventurous spirit. So take a risk. Be prudent. Don't wait for social scientists to flip a coin on your behalf. Choose heads.

NYTIMES

• Arthur C. Brooks is president of the American Enterprise Institute and an NYTimes contributing opinion writer.