Why 'Jupiter dasha' doesn't automatically mean good luck.
Earlier you learned about natural benefic/malefic — Jupiter and Venus are benefics, Saturn and Mars and the rest are malefics. But here's a twist: A natural benefic doesn't always play a good role for you.
The secret is your Lagna. Depending on what your Lagna is, the same planet ends up ruling a different Bhava, and the character of that Bhava determines whether that planet is actually good for that person or not (functional benefic/malefic). If it rules a favorable house (Trikona 1, 5, 9), it becomes a Functional benefic; if it rules a difficult house (6, 8, 12), it becomes a Functional malefic.
In particular, if a planet rules both a Kendra (1, 4, 7, 10) and a Trikona (1, 5, 9), that planet becomes the very best benefic, called the Yogakaraka. This Yogakaraka differs by Lagna — for example, Mars is the Yogakaraka for Cancer and Leo Lagnas, while Saturn is the Yogakaraka for Libra and Taurus Lagnas.
Knowing this, you break free of simplistic readings. It's not "Jupiter Dasha always means fortune, Saturn Dasha always means hardship." Depending on which Bhava that planet rules in your Lagna and what condition it's in, the outcome of a Dasha changes completely. For some people, Saturn is actually their Yogakaraka, and a Saturn Dasha becomes the best stretch of their life.
This content is for reference and entertainment, based on traditional Chinese metaphysics and astrology.