Learn English – “Live life to the fullest” what does it mean

The human mind has a natural tendency to make metaphors to describe abstract concepts. In English, one such metaphor is

"up" = good, in working order
"down" = bad, broken

Examples:

• Is the mail server up?
  The server went down yesterday when the hard disk crashed.

• The dictatorship rose to power in 1969.
  The regime fell as a result of the coup d'état in 1974.

• In the heyday of the motor industry, things were looking up.
  However, since the collapse of the motor industry, Detroit has gone downhill.

• He hit rock bottom when an alcoholic binge landed him in the emergency room.
  He has since rebounded.

• Management approved proposal A, but gave a thumbs down to proposal B.

Combine that with the arbitrary convention to orient maps with north pointing up and south pointing down, and you get an idiomatic expression "going south", meaning "turning bad".

Note that these metaphors are not always generalizable. For example, going uphill is not the opposite of going downhill. ("Uphill" usually refers to some kind of struggle.) Similarly, "going north" is not a commonly accepted expression. However, it is possible to say

Profits are expected to be north of $3 million this year.

… meaning "above 3 million dollars".

In this case, 'lives down' means a neighbor (in this case the virgin), probably within an appartment complex, whose door shares an internal hallway with your own. You would say that said neighbor 'lives down the hall' from you. You run into this phrase at work or schools as well when telling someone to go further 'down the hall' to find the door to their office or classroom. A hotel also would be a place where this phrase could apply as well.

You may also see 'a few doors down' or even possibly 'up the hall' to mean the same thing, though 'up the hall' feels to me like the direction specified is going the opposite direction than what is expected.