The Shadow out of Time
By H. P. Lovecraft 1936

"There is reason to hope that my experience was wholly or partly an hallucination—for which, indeed, abundant causes existed. And yet, its realism was so hideous that I sometimes find hope impossible. If the thing did happen, then man must be prepared to accept notions of the cosmos, and of his own place in the seething vortex of time, whose merest mention is paralysing.
If that abyss and what it held were real, there is no hope. Then, all too truly, there lies upon this world of man a mocking and incredible shadow out of time. But mercifully, there is no proof that these things are other than fresh phases of my myth-born dreams."

The Shadow out of Time By H. P. Lovecraft - Full Story Text

Howard Phillips Lovecraft (1890–1937)