Rahu and Ketu Karma 
 

Rahu and Ketu are the forces of karma and freewill that pull us into a body so that we may experience our karma and evolve toward that state where desires cease and perfection is realized. Freewill today is our karma tomorrow. Rahu is the main subconscious force of desire that we are struggling with in this life and Ketu the lessons we are trying to finish from previous lives. They are always opposite each other in the chart. They will reside in a house and sign and may also join other planets.
Rahu will obsess over all it is associating with as a way to bind us to those areas of life so we will learn those lessons. Ketu will withdrawal from the things he is associated with as those are recently learned lessons or areas of life where we are developing detachment. Where Ketu is there can be a sense of feeling used up in that area of life. The Houses of Nodal location show the areas of life affected, the signs show the mental quality of this affectation.
Having just learned these things in previous lives, Ketu will not put much effort into them, yet he will have much skill and understanding with them and an expectation of fulfillment in that area, in spite of the neglect. Still, Ketu's shows where we must finish a cycle of karma, so there is still work left to be done with where he is.

Rahu and Ketu Aspects

It has been my experience that the Nodes exert more influence when conjoined a planet than when affecting it by aspect. This is a controversial subject and others may differ with this opinion. Parashara does not address the topic directly, but I think it can be inferred that what I have stated is true.
There are certain avasthas that state a planet is harmed when conjoined a Node, (or Saturn or Mars) which seem to back this claim. Also, these same group of avasthas do not even assign Rahu and Ketu an aspectual value in virupas as they are shadow planets, not planets with a form. (Avasthas are ways to measure planetary strength)
In the classics Rahu and Ketu are mainly ignored in this way. Planets affect THEM by (planetary) aspect but not the other way around.
The Nodes are shadows, a shadow casting an aspect itself is hard to fathom. However a node in a certain sector of Sky (a rashi or sign) will affect that sign and that SIGN will cast an aspect. (called a rashi aspect) I feel that the nodes will project their influence through rasi aspect in a secondary way to the sign they are occupying and planets in those aspected rashis will be affected. But I do not think this influence is as strong as what the node affects through House / Sign and Planetary conjunction.