What this rule checks
Your Rahu is in the 1st house. Rahu is about ambition and desire. The 1st house is about you, your body and how others see you. 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.