To keep on filling
is not as good as stopping.
Overfilled, the cupped hands drip,
better to stop pouring.

Sharpen a blade too much
and its edge will soon be lost.
Fill your house with jade and gold
and it brings insecurity.
Puff yourself with honor and pride
and no one can save you from a fall.

Retire when the work is done;
this is the way of heaven.

-Tao te ching (9th verse, as translated by Dr. Wayne W. Dyer)

Also, good article...

http://www.jpost.com/servlet/Satellite?cid=1214726164944&pagename=JPost%2FJPArticle%2FShowFull

The author, Rabbi Shmuley, talks about the four unforgivable sins in the United States: killing your wife, molesting a child, being old and having too many children. He expands on the latter.