Priorities

At a lecture at university the prof takes some rocks out of a box and places them in a jar on his desk. When they're up to the rim, he asks the class if they see the jar as full, and they agree that it's full.
He then reaches into another box and takes out a bunch of pebbles and pours them into the jar, and they fall between the spaces left by the larger rocks, and again asks the class if the jar is now full, and again they agree that the jar is now full.
He reaches into another box and takes out some sand and pours it into the jar, and the sand fills up the smaller spaces between the pebbles. He again asks the class if the jar is full, and again, they agree that the jar is indeed full.
He then explains what he's trying to tell them:
"Yes, the jar is now full. The rocks symbolize the most important things in life, like your relationship between you and your spouse, your children and the people closest to you, as well as your health and your ethics and morals. The pebbles symbolize the things that are also important, like your friends, job, your neighbours, the people you deal with daily, etc. The sand symbolizes less important things that also affect your life, but to a much lesser degree, things like your hobbies, politics, what kind of car you drive, where you go on vacation, etc. If you fill the jar with sand first, you won't be able to add pebbles, let alone rocks. In order for you to have a full life, you have to have your priorities in order", he explains, "take care of the most important things first, and the others will fall into place."
At that point one of the students takes a bottle of beer out of his back pack, goes up and empties it into the jar, and of course it disappears into the sand.
"There", he says, "Now it's full."
The moral of the story - regardless of how full your life is, there's always room for beer.