You are not wrong, who deem
That my days have been a dream;
Yet if hope has flown away
In a night, or in a day,
In a vision, or in none,
Is it therefore the less gone?
All that we see or seem
Is but a dream within a dream.

"A Dream Within a Dream" (1849).

The Works of the Late Edgar Allan Poe/Volume 2/A Dream within a Dream