A booklet on Shmiras Habris in English, based on Chazal and on the teachings of Rav Nachman of Breslov.
"Spirit of foolishness"

In reality, all temptations are truly pointless and never satisfying. The strong urges one has are foolish. These seemingly “real” and “important” urges can be compared to the following parable. A man raced through a crowd of people shouting “See what I have in my closed fist!” Everyone ran after him thinking that all their desires were contained in that clenched hand. In the end, the man opened his fist and it was empty. So too, all our desires seem to have substance, but in the end we find that they are all empty dreams (Ibid. 6).

One’s mind is the ultimate weapon in this battle. One needs to flee from temptation, which is a spirit of foolishness, into da’as. Even the smallest amount of da’as which is inherent in one’s soul is enough to overcome the most powerful temptations. When one meditates on Hashem, one’s purpose in life, and the fleeting reality of this world, one realizes how foolish and insane our desires truly are. The Gemara says “A person does not sin unless a foolish spirit enters him” (Sotah 3a), (Ibid. 51; Likutey Moharan 72).

For a small pleasure lasting but a short moment one can lose all of this world and the next (Likutey Moharan II 108).