Billionaire investor Warren Buffett is famous for imparting worldly wisdom to demonstrate the core investment and life strategies that have made him one of the world's wealthiest people. 

Speaking to University of Southern California students in a 1994 commencement speech, his lifelong partner at Berkshire Hathaway, Charlie Munger, shared a story about a lesson Buffett loves to teach at business schools. 

Buffett's "20-slot" rule

According to Munger's account, Buffett likes to tell students, "I could improve your ultimate financial welfare by giving you a ticket with only 20 slots in it so that you had 20 punches--representing all the investments that you got to make in a lifetime. And once you'd punched through the card, you couldn't make any more investments at all."

"Under those rules," says Buffett, "you'd really think carefully about what you did and you'd be forced to load up on what you'd really thought about. So you'd do so much better."

Munger tells the USC students, "To me, it's obvious that the winner has to bet very selectively. It's been obvious to me since very early in life. I don't know why it's not obvious to very many other people."

The reason it's not obvious to more people is that so often we start and stop what we think are great ideas that really aren't so great after all. We may bet on 20 great ideas in our lifetime--if we even get that many--and wrongly assume they will turn profitable. Buffett says "three or five or seven" might make you wealthy, "but what you can't do is get rich by trying one new idea every day."

This Buffett rule of filtering out most good ideas (in favor of one or two great ones) is a useful life application outside of money and investing. It forces us to focus--something Buffett is very familiar with. He once said: "The difference between successful people and really successful people is that really successful people say no to almost everything."

Too often, we come across tempting distractions disguised as "another great idea." One former business acquaintance of mine was known for pursuing one--supposedly--great idea after another, but he never actually followed through on his commitments. Instead, he typically left projects half-finished before chasing after his next interest or "good idea."

Force yourself to load up

The strength of Buffett's 20-slot rule lies in "forcing yourself to load up." In other words, as Buffett has taught, whatever idea you've really put serious thought into for years or maybe even decades--those things you've researched, invested in, and diligently prepared yourself for--they should be the primary focus of all your energy and motivation.

When you "load up" on turning a simple good idea into an exceptionally great one, you're showing the uncommon persistence most people with merely good ideas lack, which is to become great at one thing, rather than good or mediocre at many.

Using Buffett's 20-slot punch card illustration, it's to wisely use each slot as a long-term stage of focused work toward achieving that one big goal. Since you only have 20 slots over a lifetime, treasure and don't misuse your punch card. For example, one slot could be a two-year phase of mastering a vital skill or habit; another to acquiring the discipline and mindset to carry out your goals.

When you resist the distractions of chasing after things that don't truly serve you and wholeheartedly direct your focus and attention to the things that do, you'll reap the returns. It's having the dedication to pouring your whole being into something long term, rather than for a short season halfheartedly. When you do, you're practicing the 20-slot rule and your odds of success will greatly improve.