At one of philosophy lectures, the professor put a really big jar on the table and filled it with couple tenis balls. Afterwards, he asked studedns if the jar was full? They all agreed...
Then the professor took a box full of small stones and poured them into the jar, afterwhich he asked again if the students thought if the jar was full? They nod with their heads looking at eachother.
The next box the professor took was filled with fine sand, the kind that you find on the beach. When he poured sand into the jar, it filled all the small holes between the stones and the tennis balls. He asked students again if the jar was full? The studends answered with "yes", whereby you could see they were all a bit confuzed by the simple question.
Then, the professor took two cups of coffee from beneth his table and poured them into the jar. The students laughted...

"Now", said the professor whlist the laughter died across the hall, "I want you to understand that this jar represents your life. Tennis balls represent all the important things in your life: your family, children, your health and your faith.
The stones are less important things in your life, such as your job, your house and your car. The sand represents all small material things in your life.
If you fill the jar with the sand first, you won't have any space for stones and tennis balls... The same goes for your life. If you spend your time on small material things only, you will never find time for important things in your life.
Take good care of things that are key to your happines. Find time to play with your kids, go to your doctor, take out your partner to dinner, visit your parents..."

One of the students raised her hand and asked what the coffee stands for? The professor smiled and said: "I'm glad that you asked that question. I've pured that coffee to show you, that no matter how full you think your life is, there is always some space for a cup of coffee with your friends".