don't go there
Don't imagine or even think such a thing. It is often used in a slightly risqué context.
Words nearby don't go there
don't cross that bridge till you come to it,
don't cry over spilt milk,
don't cut off your nose to spite your face,
don't fire until you see the whites of their eyes,
don't give up the ship,
don't go there,
don't hide your light under a bushel,
don't hold your breath,
don't judge a book by its cover,
don't know,
don't let the grass grow under one's feet