In "The Alchemist," what point does the old man’s story about the boy in the castle and the drops of oil make?

The point of Melchizedek's story is that “secret of happiness is to see all the marvels of the world, and never to forget the drops of oil on the spoon.”  What he means is that when the boy in the story was first sent out to walk about the castle, he is warned not to spill a drop of oil from the spoon he carried with him.  The boy was so paranoid about spilling the oil that he never saw the beauty of the castle or its riches.  The second time the boy is sent out, he is told to make sure to pay attention to what is around him, while still carrying the spoon with drops of oil in it.  Unfortunately, this time he got so caught up in the beauty and riches that he forgot about the oil, and it spilled.  The point of the story is to find balance.  Pay attention to what is going on around you, but don't forget to pay attention to what you are doing at the same time.