When I first learned Astrology I was told Jupiter was the best thing under the Sun, pun intended. Oh, where you see Jupiter you see nothing but happy happy joy joy, was the general consensus. Then I started to look at some charts. I have a friend with Jupiter in her sixth house - the house of health. If that theory held she should be a picture of robust health. In reality she is the person who gets the one disease in a million or the one complication that no one ever gets. Then I noticed that when Jupiter was transiting my sixth house I got cold after cold and my one sinus infection per year turned into three that year. What is it with you Jupiter?
As usual the easy explanation is rarely right. Yes, Jupiter is usually a harbinger of good things. However, as with all things Jupiter has a shadow and that is that it makes everything bigger. Someone with too much Jupiter in their chart can be a gambler or terrible risk taker with money because they think they will always be lucky even when the odds are against them. So Jupiter run amuck is not always a wonderful thing.
I have also learned to look for Jupiter as a harbinger of death. Saturn in the 8th - Pluto there as well usually portend death but so can Jupiter - as the spring board of something bigger - a life beyond.
As are all things, planets are not black or white, they are nuanced - even big, robust, loopy Jupiter.