obsess
This word conveys a sense of mental entrapment where a single thought or desire consumes the individual's attention. It carries a strong negative connotation of imbalance, suggesting that the preoccupation is unhealthy, compulsive, or disruptive to one's well-being. In modern usage, the intransitive form followed by over is the most frequent pattern, often describing a meticulous or anxious focus on minutiae. The transitive use is more formal and describes the external force of an idea dominating a person's psyche.
Meanings
To preoccupy or dominate the mind of someone to an unhealthy or extreme degree.
"The thought of failure began to obsess him during the final exams."
To think about something constantly and intensely, often to a point of irrationality or dysfunction.
"She tends to obsess over every single detail of the wedding planning."