Because our body's immune system is self-regulating and self-repairing, people who are often sick exercise their immune system, and they can build a firewall inside their bodies to guard against the invasion of viruses and bacteria. People who are not sick tend to have a loose immune system, and once a large pathogen invades, it will cause disorder in the body. Generally speaking, it is best to stay healthy all the time, which requires us to be responsible for our own health, get rid of those bad living habits, have physical examinations on time, and pay attention to the subtle changes in our bodies.