I'm a disease to you

You're finally getting there,
getting back
to being good again,
somewhere where
you're content,
and not hurting as much.
But then you drink
from my vial of
words,
and I become
a poison in your guts.
I'm just no good you see,
I hurt you but
you do nothing but good for me.
I must be like a virus
some kind of disease,
I make you weak
and damage you're heart.
I guess this means we should part,
only I don't want you to go,
you're all I have left
of the good times of old.