People come in all different shapes, sizes, personalities, styles and backgrounds. Culture, regions, family clans, and beliefs topple on top of those many built in differences. So as a consequence communication styles, problem-solution assessments and skills, judgments of right and wrong, anxiety management, and needs and wants are all unique as well. Now bundle those differences into a friendship and likely you will have interesting times expanding and exploring. Somehow though, bundle those up into a a long term, intimate relationship where you also need to be functioning as a unit (marriage for instance) and those differences are hugely impactful and likely to cause conflicts. Mutual tolerance, good will, sense of humor , mutual trustworthiness and intents/actions of respect help navigate those conflicts. But even the expression of these last 5 qualities might be expressed differently (i.e. respect does not look the same to everyone nor is a sense of humor the same). Therefore, as a consequence, tolerance of differences needs to be a key component helping you navigate close relationships.