A philosophy professor once stood in front of his class with a large empty mayonnaise jar in his hand. He stuffed the jar full of large rocks and asked his students if it was full.
His students were all in agreement that the jar was full.
He then filled the jar with small pebbles and gave it a thorough shake to disseminate the pebbles among the larger rocks. "Is the jar full now?" he inquired again.
The students all agreed that the jar remained full.
The professor then poured sand into the jar to fill in any remaining gaps.
The students then agreed that the jar was full once more.
In this story, the jar represents your life, and the rocks, pebbles, and sand are the items that fill it. The rocks represent your most important projects and activities, such as spending time with your family and staying healthy. This means that even if the pebbles and sand were to disappear, the jar would still be full and your life still be significant.
The pebbles represent the things in your life that are important but could be done without. The pebbles are obviously items that offer significance to your life (such as your work, house, interests, and friendships), but they are not essential for you to live a meaningful existence. These things come and go and are neither permanent nor necessary to your overall well-being.
The sand represents your life's remaining fillers and material possessions. This could include activities as simple as watching television, browsing your favourite social media site, or running errands. These things don't matter much in the grand scheme of things, and they're probably only done to pass the time or complete minor tasks.
The metaphor here is that if you begin by filling the jar with sand, there will be no room for rocks or pebbles. This is true for the things you allow into your life. If you spend all of your time on trivial and unimportant matters, you will run out of time for the things that are truly important.
Pay attention to the "rocks" if you want to live a more successful and efficient life, since they are crucial to your long-term well-being.