How did self-imposed isolation act as a beneficial factor in the development and longevity of chinese society?

Classical Chinese societyHow did self-imposed isolation act as a beneficial factor in the development and longevity of chinese society?
Japan did it as well, and the two are radically different in modern times.How did self-imposed isolation act as a beneficial factor in the development and longevity of chinese society?
Isolated China didn't have Brits injecting opium in their culture.