Kaal Sarp Yog is a phase where all the prime planets (Sun, Mercury, Venus, Mars, Jupiter, Saturn, and Moon) are situated between Rahu & Ketu to put harm on individuals. When all these planets are under Rahu and Ketu, then that individual undergoes through a lot of struggle and challenges in life during that period.
This yog most affects those primary areas of life like relationships, marriage, health, education, wealth that people observe while achieving the growing tolls in their life. This yog could appear as a constant struggle even when people have talent and hard work in them, but yet they do not achieve those results.
There involves 2 Kaal Sarp Yog types-
Savya Kaal Sarp Yog, where all planets are in between Raahu (head) and Ketu (tail) moving towards the tail
Apasavya Kaal Sarp Yog is the opposite where planets are between Ketu and Raahu moving towards the head
People who were born under kaal sarpa yog types have lived happily but the interesting point is that most of them had girl children born in their family who later have struggled in their lives to make it big. Also to note is that when Kaal Sarpa Yog happens, it creates multiple opportunities along with the mistreatment occurred, so that an individual may come up better with time.