Philosophy of Rocks

A philosophy professor stood before his class and had some items in front of him. When class began, he wordlessly picked up a large empty mayonnaise jar and proceeded to fill it with rocks right to the top, rocks about 2" diameter.
He then asked the students if the jar was full?
They agreed that it was.
So the professor then picked up a box of pebbles and poured them in to the jar. He shook the jar lightly. The pebbles, of course, rolled into the open areas between the rocks.
He asked his students again if he jar was full?
They agreed that yes, it was.
The professor then picked up a box of sand and poured it into the jar. Of course, the sand filled up everything else.
"Now," said the professor, "I want you to recognize that this is your life. The rocks are the important things - your family, your partner, your health, and your children - anything that is so important to you that if it were lost, you would be nearly destroyed. The pebbles are the other things in life that matter, but on a smaller scale. The pebbles represent things like your job, house, or car. The sand is everything else, the small stuff."
"If you put the sand or the pebbles into the jar first, there is no room for the rocks. The same goes for your life. If you spend all your energy and time on the small stuff, material things, you will never have room for the things that are truly most important.