One day, a philosophy professor stood before his class with a large empty jar. He filled it with big stones and asked, “Is it full?”

The students said, “Yes.”

Then he poured small pebbles into the jar, shaking it lightly. The pebbles filled the gaps.

“Is it full now?” he asked.

“Yes,” they replied.

Then he poured sand in, filling every space left.

Finally, he poured water into the jar. The professor smiled and said, “This jar is your life. The big stones are the most important things—family, health, and dreams. The pebbles are the smaller things—job, school, house. The sand is everything else—small worries and details. If you fill the jar with sand first, there’s no room for stones.”