Why can the phrase "the sincerity of adults is hidden in jokes" cause a lot of people to curse?

A sentence I read before is very suitable for answering this question. As an adult, "people's hearts are rivers and lakes" also has a great curse on this sentence, so I will answer it from my own point of view.

Junior high school is a class with good class spirit and good grades, so there are many like-minded friends. At that time, it was pure happiness, studying together in class and playing together after class. It was pure. Because everyone's unhappiness will be said directly, and if they don't like it, they will be written on their faces. So we can clearly know their attitude towards you, even if we leave, we will say goodbye well, and we don't have to worry that our sincerity will be disappointed, because we simply have strong self-healing ability and good forgetting ability. Most things are not in my heart, and I always exchange my heart for my true feelings.

Later, after going through high school and then going to college, it is obvious that some people who feel good about their relationship suddenly broke up. There is a feeling of being abandoned at this time. In fact, it was not abandoned, but was not accepted from the beginning. If it weren't for the environment at that time, my life might not have crossed. When the truth is rubbed on the ground by reality, will you seriously say something you don't care about? Imagine that you have a crush on a very good friend. If you say it directly, you will face the risk of burning your feelings for many years. Things like this can't be hidden, so it's the best choice to express your sincerity with a joke.

As an adult, the more hurt I am, the more I love to hide my sincerity in jokes. The more you lose, the more you worry that your sincerity will become a joke. We wander in people's minds, but we don't know where to live. Maybe only when we feel safe enough will we be willing to expose our hearts. The sincerity hidden in the paragraph is a subtle expression and a cautious temptation. Most adults are poor people with stories.