1
general::
Phrase(s): *in a rut
Fig. in a type of boring habitual behavior. (As when the wheels of a buggy travel in the ruts worn into the ground by other buggies making it easiest to go exactly the way all the other buggies have gone before. *Typically: be ~; get ~.) • My life has gotten into a rut. • I try not to get into a rut., Phrase(s): (stuck) in a rut
Fig. kept in an established way of living or working that never changes. • David felt like he was stuck in a rut, so he went back to school. • Anne was tired of being in a rut, so she moved to Los Angeles.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
In a settled or established habit or course of action, especially a boring one. For example, We go to the seashore every summer? we're in a rut, or After ten years at the same job she says she's in a rut. This expression alludes to having a wheel stuck in a groove in the road. [Early 1800s]
American Heritage Idioms