The disciple said to his master: “I have spent most of the day thinking about things I should not be thinking about, desiring things I should not desire and making plans I should not be making.” The master invited the disciple to take a walk with him through the forest behind his house. Along the way, he pointed to a plant, and asked the disciple if he knew its name. “Belladonna,” said the disciple. “It can kill anyone who eats its leaves.” “But it cannot kill anyone who simply observes it,” said the master. “Likewise, negative desires can cause no evil if you do not allow yourself to be seduced by them.”
In Maktub by Paulo Coelho.