"When Ravana lay dying, Rama directed his brother, Lakshamana, to go to him and learn from him the secrets of successful statecraft. Ravana taught him that a king who is eager to win glory must suppress greed as soon as it lifts its head, and welcome the smallest chance to do good to others, without the slightest procrastination. He (Ravana) had learnt the lesson through bitter experience. Greed arises from attachment to the senses and catering to them. Put them in their proper place; they are windows for knowledge, not channels of contamination.
http://devdutt.com/articles/ramayana/this-was-ravan-too.html
http://devdutt.com/articles/ramayana/this-was-ravan-too.html