udrey Hepburn was an icon.

Rising to fame in the 1950s, she was one of the greatest actresses of her era. In 1953, Hepburn became the first actress to win an Academy Award, a Golden Globe Award, and a BAFTA Award for a single performance: her leading role in the romantic comedy Roman Holiday.

Even today, over half a century later, she remains one of just 15 people to earn an “EGOT” by winning all four major entertainment awards: Emmy, Grammy, Oscar, and Tony. By the 1960s, she was averaging more than one new film per year and, by everyone’s estimation, she was on a trajectory to be a movie star for decades to come.

But then something funny happened: she stopped acting.

Despite being in her 30s and at the height of her popularity, Hepburn basically stopped appearing in films after 1967. She would perform in television shows or movies just five times during the rest of her life.

Instead, she switched careers. She spent the next 25 years working tirelessly for UNICEF, the arm of the United Nations that provides food and healthcare to children in war-torn countries. She performed volunteer work throughout Africa, South America, and Asia.

Hepburn’s first act was on stage. Her next act was one of service. In December 1992, she was awarded the Presidential Medal of Freedom for her efforts, which is the highest civilian award of the United States.

We will return to her story in a moment.

Efficient vs. Effective

You get one, precious life. How do you decide the best way to spend your time? Productivity gurus will often suggest that you focus on being effective rather than being efficient.

Efficiency is about getting more things done. Effectiveness is about getting the right things done. Peter Drucker, the well-known management consultant, once encapsulated the idea by writing, “There is nothing so useless as doing efficiently that which should not be done at all.”

In other words, making progress is not just about being productive. It’s about being productive on the right things.

But how do you decide what the “right things” are? One of the most trusted approaches is to use the Pareto Principle, which is more commonly known as the 80/20 Rule.

The 80/20 Rule states that, in any particular domain, a small number of things account for the majority of the results. For example, 80 percent of the land in Italy is owned by 20 percent of the people. Or, 75 percent of NBA championships are won by 20 percent of the teams. The numbers don’t have to add up to 100. The point is that the majority of the results are driven by a minority of causes.

The Upside of the 80/20 Rule

When applied to your life and work, the 80/20 Rule can help you separate “the vital few from the trivial many.”

For example, business owners may discover the majority of revenue comes from a handful of important clients. The 80/20 Rule would recommend that the most effective course of action would be to focus exclusively on serving these clients (and on finding others like them) and either stop serving others or let the majority of customers gradually fade away because they account for a small portion of the bottom line.

This same strategy can be useful if you practice inversion and look at the sources of your problems. You may find that the majority of your complaints come from a handful of problem clients. The 80/20 Rule would suggest that you can clear out your backlog of customer service requests by firing these clients.

The 80/20 Rule is like a form of judo for life and work. By finding precisely the right area to apply pressure, you can get more results with less effort. It’s a great strategy, and I have used it many times.

But there is a downside to this approach, as well, and it is often overlooked. To understand this pitfall, we return to Audrey Hepburn.

The Downside of the 80/20 Rule

Imagine it is 1967. Audrey Hepburn is in the prime of her career and trying to decide how to spend her time.

If she uses the 80/20 Rule as part of her decision-making process, she will discover a clear answer: do more romantic comedies.

Many of Hepburn’s best films were romantic comedies like Roman Holiday, Sabrina, Breakfast at Tiffany’s, and Charade. She starred in these four films between 1953 and 1963; by 1967, she was due for another one. They attracted large audiences, earned her awards, and were an obvious path to greater fame and fortune. Romantic comedies were effective for Audrey Hepburn.

In fact, even if we take into account her desire to help children through UNICEF, an 80/20 analysis might have revealed that starring in more romantic comedies was still the best option because she could have maximized her earning power and donated the additional earnings to UNICEF.

Of course, that’s all well and good if she wanted to continue acting. But she didn’t want to be an actress. She wanted to serve. And no reasonable analysis of the highest and best use of her time in 1967 would have suggested that volunteering for UNICEF was the most effective use of her time.

This is the downside of the 80/20 Rule: A new path will never look like the most effective option in the beginning.

Optimizing for Your Past or Your Future

Here’s another example:

Jeff Bezos, the founder of Amazon, worked on Wall Street and climbed the corporate ladder to become senior vice-president of a hedge fund before leaving it all in 1994 to start the company.

If Bezos had applied the 80/20 Rule in 1993 in an attempt to discover the most effective areas to focus on in his career, it is virtually impossible to imagine that founding an internet company would have been on the list. At that point in time, there is no doubt that the most effective path—whether measured by financial gain, social status, or otherwise—would have been the one where he continued his career in finance.

The 80/20 Rule is calculated and determined by your recent effectiveness. Whatever seems like the “highest value” use of your time in any given moment will be dependent on your previous skills and current opportunities.

The 80/20 Rule will help you find the useful things in your past and get more of them in the future. But if you don’t want your future to be more of your past, then you need a different approach.

The downside of being effective is that you often optimize for your past rather than for your future.

Where to Go From Here

Here’s the good news: given enough practice and enough time, the thing that previously seemed ineffective can become very effective. You get good at what you practice.

When Audrey Hepburn dialed down her acting career in 1967, volunteering didn’t seem nearly as effective. But three decades later, she received the Presidential Medal of Freedom—a remarkable feat she is unlikely to have accomplished by acting in more romantic comedies.

The process of learning a new skill or starting a new company or taking on a new adventure of any sort will often appear to be an ineffective use of time at first. Compared to the other things you already know how to do, the new thing will seem like a waste of time. It will never win the 80/20 analysis.

But that doesn’t mean it’s the wrong decision.

Garry Kasparov and his long-time rival Anatoly Karpov—two of the greatest chess players of all-time—took their respective seats around the chess board. The 1990 World Chess Championship was about to begin.

The two men would play 24 games to decide the champion with the highest scoring player being declared the World Chess Champion. In total, the match would stretch for three months with the first 12 games taking place in New York and the final 12 games being played in Lyon, France.

Kasparov started off well, but soon began to make mistakes. He lost the seventh game and let multiple victories slip away during the first half of the tournament. After the first 12 games, the two men left New York with the match tied at 6-6. The New York Times reported that “Mr. Kasparov had lost confidence and grown nervous in New York.”

If Kasparov was going to retain his title as the best in the world, it was going to take everything he had.

“Playing Kasparov Chess”

Josh Waitzkin was a chess prodigy as a child and won multiple U.S. Junior Championships before the age of 10. Along the way, Waitzkin and his father had the opportunity to connect with Garry Kasparov and discuss chess strategy with him. In particular, they learned how Kasparov dealt with remarkably difficult matches like the one he faced against Karpov in the 1990 World Chess Championship.

Waitzkin shares the story in his book, The Art of Learning (audiobook).

Kasparov was a fiercely aggressive chess player who thrived on energy and confidence. My father wrote a book called Mortal Games about Garry, and during the years surrounding the 1990 Kasparov-Karpov match, we both spent quite a lot of time with him.

At one point, after Kasparov had lost a big game and was feeling dark and fragile, my father asked Garry how he would handle his lack of confidence in the next game. Garry responded that he would try to play the chess moves that he would have played if he were feeling confident. He would pretend to feel confident, and hopefully trigger the state.

Kasparov was an intimidator over the board. Everyone in the chess world was afraid of Garry and he fed on that reality. If Garry bristled at the chessboard, opponents would wither. So if Garry was feeling bad, but puffed up his chest, made aggressive moves, and appeared to be the manifestation of Confidence itself, then opponents would become unsettled. Step by step, Garry would feed off his own chess moves, off the created position, and off his opponent’s building fear, until soon enough the confidence would become real and Garry would be in flow…

He was not being artificial. Garry was triggering his zone by playing Kasparov chess.

—Josh Waitzkin, The Art of Learning

When the second half of the World Chess Championship began in Lyon, France, Kasparov forced himself to play aggressive. He took the lead by winning the 16th game. With his confidence building, he rattled off decisive wins in the 18th and 20th games as well. When it was all said and done, Kasparov lost only two of the final 12 games and retained his title as World Chess Champion.

He would continue to hold the title for another 10 years.

“Fake It Until You Become It”

It can be easy to view performance as a one-way street. We often hear about a physically gifted athlete who underperforms on the field or a smart student who flounders in the classroom. The typical narrative about underachievers is that if they could just “get their head right” and develop the correct “mental attitude” then they would perform at the top of their game.

There is no doubt that your mindset and your performance are connected in some way. But this connection works both ways. A confident and positive mindset can be both the cause of your actions and the result of them. The link between physical performance and mental attitude is a two-way street.

Confidence is often the result of displaying your ability. This is why Garry Kasparov’s method of playing as if he felt confident could lead to actual confidence. Kasparov was letting his actions inspire his beliefs.

These aren’t just feel-good notions or fluffy self-help ideas. There is hard science proving the link between behavior and confidence. Amy Cuddy, a Harvard researcher who studies body language, has shown through her groundbreaking research that simply standing in more confident poses can increase confidence and decrease anxiety.

Cuddy’s research subjects experienced actual biological changes in their hormone production including increased testosterone levels (which is linked to confidence) and decreased cortisol levels (which is linked to stress and anxiety). These findings go beyond the popular fake it until you make it philosophy. According to Cuddy, you can “fake it until you become it.”