If the planetary situation isn't good with your horoscope or the stars aren't in your favor then this puja is strongest. Nav Chandi yagya is The mix of a thousand mantras which happen to be exported form Markandeya Purana. In Markandeya Purana, you will find various mantras for different troubles. https://www.youtube.com/watch?v=QIX0JZlLsgE