Be a ghost of (someone or something's) former self informal verb phrase
To be weaker or inferior in contrast to how someone or something used to be, frequently as a result of negative circumstances.
The old house, which had once been so full of life, was now just a ghost of its former self.
After her illness, Anna was a ghost of his former self.
Her once strong memory is gone and she is now a ghost of her former self.
To not be as healthy, strong etc as one formerly was
The verb "be" should be conjugated according to its tense.