Rahu and Ketu will represent the Sign / House occupied by them in your Chart, provided they are not associated with any other planets. They have the right and the power to modify the outcome.
Whenever their main or sub-periods are active in the Vimshottari Dasha, look for the adjacent period lords and check if they have any association with these lords due to the House / Sign / Star or Sub.
Try and imagine that the star portion in a Sign is a container by itself and if Rahu and another planet occupy or are contained in this star, then Rahu can and will preside over the other planets functionality in total and whenever such associated planet comes as an adjacent period lord Rahu will provide the functionality instead of the said planet.
If the houses owned by the adjacent planet are favorable then it will act in a manner of enhancing or blowing out of proportion the effect of such houses. Rahu being a deceptive entity it cannot grant satisfaction and hence you will be left with a feeling of dis-satisfaction as Rahu multiplies, enhances or blows out of proportion all the effects. It is a force multiplier which leaves one tired and frustrated to some extent.
Rahu & Ketu are the two imaginary points of intersection formed when the Plane of Moon's Orbit intersects the plane of the Sun's Orbit. The point of intersection in the North is called as Moon's North Node and the point in the South is called as the Moon's South Node. Moon's North Node is called as Rahu or Ascending Node and Moon's South Node is called as Ketu or Descending Node
Since Rahu & Ketu are the resultants of the computed elements based on Sun & Moon. The Sun which represents the Spirit whereas Moon represents the Mind. The active or over-active part is Rahu whereas Ketu is the inactive or the passive element. The proximity or association of other planets with them represents the overall attitude in the chart.
In the chart, analyze their positions first, then check whether Rahu's Dasha is in the active age of the chart owner and if Rahu is associated with planets owning favorable houses or are occupying such houses in the chart then such a persons life will undergo struggle or a fight. In other words such a chart owner will be active and dynamic in nature and actions.
If Ketu's dasha is in the latter part of life and if Ketu is associated with planets owning favorable houses or placed favorably then that part of life could be passive or inactive.
Rahu and Ketu