Rahu and Ketu both represent illusion. In their dashas, they create illusion related with the house where they are sitting. We would be under one or the other illusion during dashas of Rahu or Ketu.
It is also interesting to note that Rahu's dasha is followed by Jupiter and Ketu's dasha is followed by Venus.
Jupiter is Brihaspati and Venus is Shukracharya. Both are Teachers. So, dashas of illusion are followed by dashas of knowledge and wisdom.
It means that as closer we get to Jupiter or Venus dasha, as the case may be, we get rid of illusion of Rahu or Ketu respectively and find wisdom.
Like, I have Rahu in 10th house and I was under illusion about my right career path throughout Rahu MD and got some direction only when I entered into last Mars AD of Rahu MD and came nearer to Jupiter MD.
Swami Premanand Bharti