shadow of one's (former/old) self, a

Also, shadow of one's former or old self . A person, group, or thing that has become weaker in physical or mental capacities or in power or authority. For example, After that long battle with the flu, he was just a shadow of his old self, or This new administration is but a shadow of itself, or The revised constitution is a shadow of its former self. The use of shadow for an emaciated person dates from the late 1500s, and by about 1800 the word began to be used for other kinds of attenuation.

Reduced or diminished, in vigor or size by age, illness, or fatigue, or in wealth or power. This term was a hyperbole for being emaciated as long ago as the sixteenth century. Later it was used for other kinds of reduced circumstances, as by Sir Walter Scott in Guy Mannering (1815): “He appeared to wither into the shadow of himself.”