set in ways
set in (one's) ways
Inflexible; unwilling to change. Grandma will never retire—she's been a teacher for 50 years and is totally set in her ways. You'll never convince him to change, he's too set in his ways now.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
set in one's ways
leading a fixed lifestyle; living according to one's own established patterns. At her age, she's getting sort of set in her ways. If you weren't so set in your ways, you'd be able to understand young people better.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.