Every transgression brings into being certain creatures, these so-called "extraneous forces."
Just as every good deed creates an angel, the essence of every wrong action causes a similar essence to come into existence.
These evil products of sin, the many unnatural offspring of man, cry out to be recognized and supported as legitimate sons.
They follow the person relentlessly, out of a sense of kinship and belonging, nurturing his remorse and exacting his punishment, unto death.
Ordinarily a person cannot obliterate them.
They exist in the worlds above and below ours, these angelic and demonic products of our deeds, and only repentance out of love can change the essence of the evil into good, the dark into light.
–Rabbi Adin Steinsaltz
From The Long Shorter Way by Rabbi Adin Steinsaltz