As soon as the pleasure enters the desire, it quenches it and fills it to that degree. A desire that is quenched stops feeling the pleasure, because the pleasure is felt inside the desire. This means that the desire itself is felt. So on the one hand, there has to be an appetite, a hunger, and on the other hand, there must be pleasure. It is only when both of them meet that one feels good. And when the desire is filled, it is turned off, it goes away to the degree of the filling, up to a point where one feels that no desire even existed. This is the form of a direct reception of pleasure, a pleasure that enters a desire. This is why we are never satiated, and we keep on searching for satisfaction.
Courtesy of http://www.youtube.com/watch?v=iaS1FmkYFh4