I want to share this story with you.
The professor puts some big round stones in the jar until it's filled by them. He asks again <<how is it now?>> and the students all say <<full>>.
The professor now adds some handfuls of small white stones that go to fill all the spaces, and asks again <<how about now?>> The students wait a second, then say<<full>>.
Finally the professor takes two glasses of wine and pours them inside, filling all the spaces left, saying <<now it's full!>>
At this point he addresses a quite stupefied class with the explanation:
<< what is the morale of this experiment? take the empty jar as a symbol of your life, and the big stones are the important things like family, love, friends, nice travels and vacations. Then the small stones are the minor things in your life, like university, job, hobbies. The sand stands for all the less important stuff, like a car, or tv. So if you fill your life starting from the less important things, you'll never have enough space for the most important ones. Always remember what is important and what is not, and never lose time on useless things>>.
At this point, one student asks: <<and what about the two glasses of wine?>>
The professor answers: <<well, there will always be time for a couple of glasses with a good friend!!!>>