How does astrology predict the success or failure of a marriage or other relationship?
According to the level of cooperation among the involved parties. Marriage or any relationship is about commitment, trust, friendship, love, partnership, and whatever other elements are appropriate to a given dynamic. Astrology shows us how to maximize ease and comfort with one another, minimize difficulty, and how to meet and overcome challenges together. Anyone can be anything they choose, take on any traits they like, but some will be inherent, others will require work, and each individual finds different things differently appropriate or inappropriate. Every person chooses also to put more or less effort into any relationship they enter, and that choice too is reflected in the outcome.