To illustrate the disastrous consequences of excessive desire, I will narrate a story. Once a wayfarer, who was making a long journey by foot in the hot sun, was feeling tired and sought the shade of a tree to rest for a while.
It so happened that the tree was a wish fulfilling tree. Sitting under its shade, he wished for a cup of cold water for quenching his thirst. To his astonishment a cup of water was placed before him. After quenching his thirst he felt that it would be good if he could get a bed to recline on and enjoy a siesta. Immediately a bed was provided from nowhere. Then he thought how nice it would be if his wife also was there. In a flash, he found his wife there.
At this stage, he had a doubt in his mind as to how his wife, who was a far away at home, could come there and thought that it might be a demon in her form which might even devour him. As he thought in this manner, it woman turned into a demon and devoured him! This is the result of excessive desire, which is the enemy within you.