a shadow of (someone's or something's) old self

A person, group, place, etc., that has become dramatically less healthy, vivacious, or robust, often following some traumatic event or negative circumstances. Tom's been nothing but a shadow of his old self ever since the accident. His bubbly, outgoing personality is gone, replaced by constant gloom and cynicism. The mass emigration of workers from the town during the recession has left it a mere shadow of its old self. The company used to be at the top of the industry, but after years of bad decisions and poor management, it's little more than a shadow of its old self now.

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.”