The Professor and the Jar

A professor of philosophy stood before his class with a brown bag in front of him. When the class began, wordlessly he took out a large empty jar and some rocks and proceeded to fill the jar with rocks. He then asked the students if the jar was full. They agreed that it was full.
The professor then took out a box of pebbles and poured them into the jar. He shook the jar lightly and …

… watched as the pebbles rolled into the open areas between the rocks. He then asked the students again if the jar was full. Again, they unanimously agreed that the jar was full.
Next, the professor took out a box of sand and poured it into the jar. The sand filled the remaining open areas of the jar. He asked once more if the jar was full. They agreed it was.
The Professor then took out a bottle of beer and poured the entire content into the jar, effectively filling the space between the grains of sand.

“Now,” said the professor, “I want you to recognize that this jar represents your life. The rocks are the truly important things, such as your health, your partner, your family, your friends. If ever else was lost and only the rocks remained, your life would still be meaningful.
The pebbles are the other things that matter in your life, like your job, your house, your car.
The sand signifies the remaining “small stuff” and material possessions.
“If you put sand into the jar first” he continued, “there is no room for the rocks or the pebbles.