In ancient Daoist books, two types of Heart Demons are described.
One type is the Evil Heart Demon, which some cultivators indulge in slaughter, destruction, death, despair, and chaos, controlled by negative emotions and losing themselves. Many demonic cultivators are lost in the bloodiness and brutality of Demon Dao.
The other type is the Good Heart Demon, which is the Heart Demon of orthodox cultivators.
Orthodox cultivators firmly believe in justice throughout their lives, acting with integrity, but when they've done certain evil deeds, they feel troubled, cannot let go, and their spirit feels guilty, gradually giving rise to a Heart Demon.
In fact, who in the world can guarantee they never commit an evil act in their lifetime?
For those at the bottom, born into low status with limited scope and development, it's still possible to ensure they do no evil in life; however, to stand at the top, one inevitably must commit evil.
Crack!
Crack!