What is the reason that couples face so many difficulties? In Germany, one in three marriages ends in divorce today. In search of answers, the authors analyzed their ten years of therapeutic work with couples. They found that it is primarily the influences from the past that make life difficult for couples—masks that were put on in childhood and are now confused with reality. These manifest in the same recurring themes: in communication and conflict patterns; in the differing perceptions of men and women; in unconsciously followed rules and projections from their families of origin; and above all, in behavioral patterns stemming from relationship traumas. The authors observed that the behavioral patterns of men and women fit together according to the key-lock principle. This is why they clash so intensely.