Wikipedia:
The non-canonical early Christian book, The Shepherd of Hermas, of around A.D. 140–150,[1] has a reference to the idea of two angels: "There are two angels with a man—one of righteousness, and the other of iniquity".[2] These angels in turn descend into a person's heart, and attempt to guide a person's emotions. Hermas is told to understand both angels, but to only trust the Angel of Righteousness. The concept is similar to ideas of personal tutelary spirits that are very common in many ancient and traditional cultures.
In some Christian folklore, each person has a dedicated guardian angel whose task is to follow the person and try to prevent them from coming to harm, both physical and moral. At the same time each person is assailed by devils, not usually considered as single and dedicated to a single person in the same way as the guardian angel, who try to tempt the person into sin. Both angels and devils are often regarded as having the ability to access the person's thoughts, and introduce ideas.
Though I would not be surprised if something similar was found in Greek mythology.
= new reply since forum marked as read