A professor walked into class one day ready to give his lecture to his students.
He pulled out a jar filled with golf balls. He asked his students if the jar was full, to which they all replied yes. He then pulled out a bag filled with little pebbles and began filling the jar with them, and the pebbles fell between the gaps held up by the golf balls. He then asked the students again, if the jar was full. Again they replied yes. He then pulled out another bag filled with sand. He poured the sand into the jar and the sand began falling between all the small air spaces upheld by the golf balls and pebbles. He asked the same question, and got the same answer.
After this, the professor pulled out 2 cups of coffee.
He began pouring the contents of both cups into the jar, and, as expected, the hot liquid easily managed to fall between the air spaces upheld by the balls, pebbles and sand.
The professor then said:
"This jar represents your life. The golf balls represent your main priorities, such as your family, your home, your job. The pebbles represent the other minor things in your life, such as your car, your clothing and your food. The sand represents things which do not take a priority in your life, such as the clothes you wear at home, the contents of your desk drawer, or what tv shows you watch. But just remember, no matter how full, how busy your life it, you always have time for a cup of coffee with a friend."