The descent to the infernal regions is easy enough, but to retrace one's steps, and reach the air above, there's the rub.

The descent to the infernal regions is easy enough, but to retrace one's steps, and reach the air above, there's the rub.

下凡到地狱是很容易的，但是要走回头路，到上面的空气里去，就有困难了。

-- Publius Vergilius Maro 维吉尔