This study tested whether each of the four main aspects of rational thinking decreased expected relationship dissatisfaction when imagining having a serious disagreement with either a romantic partner or closest friend. The four features, common to cognitive theories of therapy, were the tendency not to exaggerate negative effects, not to demand that one's wishes should always be met, not to globally rate individuals or relationships and not to over-generalise that these experiences always have happened or will happen. Only when combined together did the four aspects significantly decrease expected relationship dissatisfaction in comparison to a control condition in which a serious disagreement was simply reiterated. This combined condition also significantly decreased the irrational tendency to agree that disagreements are destructive.