What this rule checks
Your Jupiter is in the 12th house. Jupiter is about growth and wisdom. The 12th house is about rest, loss, foreign lands and spirituality. Source: Phaladeepika, chapter 8 (a classic text), slokas 14 to 16. 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.