Warren Buffett knows that the greatest commodity of all is time. Buffett once told us that "the difference between successful people and really successful people is that really successful people say no to almost everything."

Whatever your level of success, one thing is certain: knowing when to say "no" to is key to controlling your life.

Seeking more practical wisdom from the Oracle of Omaha, I ran into a story where Buffett, supposedly, gave his personal pilot Mike Flynn a powerful coaching lesson on how to prioritize his life's goals. Intrigued by Buffett's three-step productivity strategy to simplify our own lives (known as the "25/5 Rule"), I'm including it below.

Buffett's 25/5 Rule

  • Step 1. Write down a list of your top 25 career goals.
  • Step 2. Circle the five most important goals that truly speak to you. These are your most urgent goals and highest priorities to focus on.
  • Step 3. Cross off the other 20 goals you have listed that hold less importance. 

Buffett was said to have told his pilot that since those 20 goals are not urgent priorities, any effort invested in them robs you of focus and energy from your five highest-priority goals.

This exercise has widely been published in books and shared in hundreds of blogs and media outlets, including Business Insider,  Lifehack, and Yahoo Finance. There was just one problem:​ the whole story was fabricated. 

That's right. Buffett never actually shared this compelling piece of advice with his personal pilot or anyone else. Ever.

Scott Dinsmore, founder and CEO of career development platform Live Your Legend, was the one who supposedly heard it first after having "met a guy who was close with one of Warren Buffett's pilots." He then published the account of Buffett's rule on his blog and we were off to the races.

Enter Alex Banayan to set us straight. Back in 2013, the author of The Third Door was on a personal quest to interview the world's most successful people to discover how they launched their careers.

Having already spoken to Buffett's bestie Bill Gates and Apple co-founder Steve Wozniak, Banayan was hot on Buffett's trail to pin the billionaire investor down for a one-on-one interview.

Fat chance. Proving this to be an impossible task, Banayan booked a flight to Omaha, Nebraska, to attend Berkshire Hathaway's 2013 shareholders meeting.

The plan? Ask Buffett the question during the Q&A portion of the event. The moment finally came and the spotlight fell on Banayan. Here's his version of the story as told to CNBC:

"Mr. Buffett, I've heard that one of your ways of focusing your energy is that you write down the 25 things you want to achieve, choose the top five and then avoid the bottom 20. I'm really curious how you came up with this and what other methods you use for prioritizing your desires?"

Buffett's response? "Well, I'm actually more curious about how you came up with it."

Awkward.

After the audience exploded in laughter, Buffett explained that he and his business partner Charlie Munger are not disciplined enough to approach decision-making in that way. "I can't recall making a list in my life," said Buffett.

Applying the rule to raise your level of success 

Does the fact that the 25/5 Rule never came from Buffett diminish its value or render it useless? Of course not. But its true worth is really dependent on each individual. It will take discipline, a strong will, and self-control to focus intently on the 5 highest priorities you want to put it into action.

Not only is Buffett's fictitious 25/5 Rule useful for clarifying your life goals and refocusing on the things that matter the most, but it's also a rule that most successful people practice.

This brings us back to what separates really successful people from the rest of the pack, according to an even better rule, based 100 percent on Buffett truth:

"They say no to almost everything."

What are you saying no to?

As you think of all the countless tasks you're likely to face this week or month, consider applying the "no" rule when going through the 25/5 exercise to raise your own productivity. Go ahead, do the list by writing down 25 things that you think you need to get done by month's end.

Next, have a moment of truth with yourself: What 20 things do I need to say no to on the list so that my focus is intently placed on the five most important goals I should absolutely say "yes" to? 

That's it. Focus all your efforts on getting these five highest priorities done at all costs, no matter what. 

When you do that, you will maximize your productivity by only spending time on the things that will propel you forward to success.