It is easy to go down into hell;
night and day the gates of dark death stand wide;
but to climb back up again, to retrace one’s steps to the open air;
there lies the problem, the difficult task.
—Virgil: The Aeneid, Book VI, line 192 (paraphrase)
More accurately:
The gates of hell are open night and day;
Smooth the descent, and easy is the way:
But to return, and view the cheerful skies,
In this the task and mighty labor lies.
William Dare 