The dictum "Sanivat rahu" means that Rahu is like Sani/saturn.
In some classical texts it is mentioned that Rahu behaves as per the lord of the house in which he is posited.
Rahu is he signifactor for our questioning nature(good for science), rule breaking/venting nature, hypocrisy n diplomacy, masking(good in cinema n drama), for potions, toxins and chemicals and also for foreign culture.
Traditionally Rahu in lagna or ascendant is considered as a difficult positioning, which makes the person brutal, selfish, conceited and unhealthy.
But i have seen many masters with Rahu in lagna, honest and straight forward.
But all these people also practice Kundalini tantra or atleast some breathing techniques.
So, i can safely assume that the ones who practice spiritual techniques don't get the negatives attributed to Rahu.
As the shadow planet which is responsible to cause grahana or eclipse of 2 life providing bodies, namely the sun and the moon, Rahu is feared a lot.
Rahu, the coiled serpent in the spine can be of tremendous advantage for all with rahu in 1, 5 or 9th house. Rahu in 1,5 and 9 is supposed to cause difficulties to children too.
Mntra for rahu:
om bhraam bhreem bhroum sa: rahuvae namaha.
kala bhairava prayers are also supposed to help.
pulse: urad dal/black gram
The story goes like:
when the asura suvarnabhanu was cut by vishnu's sudarsana chakra, (giving 2 forms as rahu n ketu) the blood that dripped down gave rise to garlic, a wonder drug, but something that provides lot of asuric qualities like suspicion.
turmeric is also used as an effective pariharam for rahu.
planting and watering turmeric plant, using it in food with prayers to rahu, is considered very positive remedy for rahu.
Rahu, like other malefic planets, is supposed to do good in upachayas, namely 3, 6, 10 and 11 houses. Rahu in dhanu is sometimes known as kodanda rahu with a benefic nature.