At the beginning of a philosophy class at a university, the professor stands up with some items that look dangerous on his desk. That's an empty mayonaisse jar, some rocks, some gravel, and sand. Students looked at these objects with curiosity. They wonder what the professor wants to do and try to guess what a demonstration will happen.
Without saying a word, the professor began laying small stones into the mayonaisse jar one by one. The students were confused, but the professor did not give an explanation first. After the rocks reached the neck of the tube, the professor spoke for the first time that day. He asked the students if they thought the jar was full. The students agreed that the jar was full.
The professor then took the pebbles on the table and slowly poured the pebbles into the jar. The small pebbles found a gap between large boulders. The professor then lightly shakes the jar to allow the pebbles to settle on the crack in the jar. He then asked the students if the jar was full, and the students agreed again that the jar was full.
The students now know what the professor will do next, but they still do not understand why the professor did it. The professor takes the sand and pours it into a jar of mayonnaise. Sand, as expected, fills every remaining space in a jar. The professor asks his disciples for the last time whether the jar is full, and the answer is once again: YES.
The professor then explains that the jar of mayonnaise is an analogy to life. He likened rocks to the most important thing in life, namely: Health, your spouse, your children, and all the things that make a complete life.
He then compares the pebbles to the things that make your life as comfortable as your job, your home, and your car. Finally, he explains sand is the little things that are not very important in your life.
Professor explained, putting the sand first in the jar will cause no room for rocks or pebbles. Similarly, disrupting your life with small things will cause you to have no room for the great things that are truly valuable.