obsession
This term describes a mental state of intense preoccupation that often borders on the compulsive. It carries a dual connotation: it can describe a passionate, driving interest that fuels achievement, or a pathological fixation that disrupts normal functioning and mental health. In a spiritual or archaic context, the word refers to the external influence of a supernatural entity. This differs from possession, where the entity is seen as having fully taken over the host, whereas obsession implies a persistent, intrusive haunting or harassment by a spirit.
Meanings
An idea or thought that continually preoccupies or intrudes on a person's mind to an extreme or unhealthy degree.
"His obsession with cleanliness meant he washed his hands every ten minutes."