There is a Chinese saying which carries the meaning that 'A speech will either prosper or ruin a nation.' Many relationships break off because of wrong speech. When a couple is too close with each other, we always forget mutual respect and courtesy. We may say anything without considering if it would hurt the other party.
A friend and her millionaire husband visited their construction site. A worker who wore a helmet saw her and shouted, 'Hi, Emily! Remember me? We used to date in the secondary school.' On the way home, her millionaire husband teased her, 'Luckily you married me. Otherwise you will be the wife of a construction worker.' She answered, 'You should appreciate that you married me. Otherwise, he will be the millionaire and not you.'
Frequently exchanging these remarks plants the seed for a bad relationship. It's like a broken egg - cannot be reversed.