run their course

• 自然地发展； 持续到自然结束

run their course的用法和样例：

例句

1. Their friendship was growing by degrees into love.
   他们的友谊正逐渐地发展成爱情。
2. Never play by their rules -- Ubuntu founder Mark Shuttleworth.
   在减劫中要逆大流地发展自己！