How to Fill a Bucket

I apologize in advance if you've already heard this story. It's an old one, but it stands repeating...

A time management expert is giving a presentation. He has a giant plastic bucket, which he fills to the brim with large stones.

"This is full, right?" Heads nod vigorously. 

He reaches under the table and brings out a bag of pebbles. He pours in as many as he can, shaking the bucket to make room.

"Is the bucket full now?" This time the nodding is a little more tentative. 

He pulls out a bag of sand and packs it in until every pocket of air has been filled.

"Now, at last, it really is full, right?"

"Yes!" comes the cry.

Yet again the teacher reaches under his desk. His hand emerges with a jug of water. He pours until, finally, the bucket overflows.