All 3 Uses

fixate
in
The Magic Mountain
(Auto-generated)

And what is this fixation he has about work?†
Chpt 4.1 *
Would you allow me"—and here Herr Settembrini bent forward on his chair, and with a smile he placed both feet on the floor, tucked his folded hands between his knees, and thrust his head forward at a slight tilt—"would you allow me," he repeated with some emotion in his voice, "to lend you a helping hand in your exercises and experiments and to play a corrective role whenever I see danger looming in the form of some pernicious fixation?"†
Chpt 5.1
The director occasionally lent Paravant a hand in his melancholy puttering, even encouraged him in the fixation.†
Chpt 7.6

Definitions:

(1) (fixate as in: fixated on football)
overly focused
(2) (meaning too rare to warrant focus)
Fixation can reference chemical bonding (especially of Nitrogen in the soil), or an arrested stage of development theorized by Freud (as in oral fixation), or (especially in medicine) the activity of fastening something firmly in position.