The most important characteristic that separates happy marriages from unhappy ones is the level of communication between partners. The best predictor of long-term relationship satisfaction and stability is the capacity for effective communication. In other words, the number of issues, unique personality features, or ideological differences have little bearing on whether a marriage is happy or unhappy. Instead, it is how couples discuss their problems and disagreements. The key is communication, and it's thought that learning communication skills is simple.