Why do people?

Not only for marriage but also for everything in our first sight we feel it better. Due to this human nature girl and a boy fall in love with each other. (For example: if we are very thirsty and at that time we feel that water is the valuable thing in the universe. This is similar in case of food and any thing. But after we quench the thirst we feel disgust at water). Like that after marriage they quench their hopes. Also some hopes cannot be feasible for them. If they are satisfied they feel the hopes are nothing. If they are unsatified by the hopes they will get despaired. This is the reason for divorce. Thanks for asking. Best question.