The Romantic poets glorified the Imagination, but they recognized its darker half. In "Strange Fits of Passion I Have Known," William Wordsworth shows the imagination's negative turn with the final line stanza:
What fond and wayward thoughts will slide
Into a Lover's head!
"O mercy!" to myself I cried,
"If Lucy should be dead!"
In Goethe's "ErlKoenig," imagination actually turns deadly (at least in my interpretation), when in the last line "The child he held in his arms was dead."
Today a more scientific mind might speak of the horrifying depths of the imagination as obsession, as a psychological issue. But I think the Romantics understood it too. And as a parent, I know this darker half of imagination. When I can visualize horrifying events, and actually sense the emotional reaction to such horrifying events (not actually experience it, but touch it, know it, sense it), I recognize the horror that our great gift of imagination can turn into.