What this rule checks
Your Rahu is in the 9th house. Rahu is about ambition and desire. The 9th house is about luck, teachers, your father and belief. Source: Phaladeepika, chapter 8 (a classic text), slokas 25 to 27. Notes beyond the classic text are the author's own modern reading. Classic texts describe this placement harshly. Read it as a tendency, not a verdict.