A philosophy professor once stood up before his class with a large empty mayonnaise jar. He filled the jar to the top with large rocks and asked his students if the jar was full.
His students all agreed the jar was full.
He then added small pebbles to the jar, and gave the jar a bit of a shake so the pebbles could disperse themselves among the larger rocks. Then he asked again, “Is the jar full now?”
The students agreed that the jar was still full.
The professor then poured sand into the jar to fill up all the remaining empty space.
The students then agreed again that the jar was full.
In this story, the jar represents your life and the rocks, pebbles, and sand are the things that fill up your life. The rocks represent the most important projects and things you have going on, such as spending time with your family and maintaining proper health. This means that if the pebbles and the sand were lost, the jar would still be full and your life would still have meaning.
The pebbles represent the things in your life that matter, but that you could live without. The pebbles are certainly things that give your life meaning (such as your job, house, hobbies, and friendships), but they are not critical for you to have a meaningful life. These things often come and go, and are not permanent or essential to your overall well-being.
Finally, the sand represents the remaining filler things in your life, and material possessions. This could be small things such as watching television, browsing through your favorite social media site, or running errands. These things don't mean much to your life as a whole, and are likely only done to waste time or get small tasks accomplished.
The metaphor here is that if you start with putting sand into the jar, you will not have room for rocks or pebbles. This holds true with the things you let into your life. If you spend all of your time on the small and insignificant things, you will run out of room for the things that are actually important.
In order to have a more effective and efficient life, pay attention to the “rocks,” because they are critical to your long-term well-being.