not practicing what one preaches; physician, heal thyself
Proverbial expression used when someone, especially an expert, fails to follow their own advice. Often applied to doctors who neglect their own health.
He's a case of 'physician, heal thyself'—always telling his patients to exercise but never doing any himself.
Similar meaning: a dyer wearing white hakama, i.e., too busy with others' work to attend to one's own. 医者の不養生 specifically refers to a doctor's neglect of their own health.
A set phrase combining 医者 (doctor) and 不養生 (neglect of health). The exact origin is uncertain, but it has been used proverbially to point out hypocrisy or inconsistency in those who give advice.