逆水行舟：谚语：‘逆水行舟，不进则退。’

As the old Chinese proverb goes, 'A boat sailing up the river must forge ahead or it will be driven back.'

（比喻 fig.）学习或做事就好像逆水行船，不努力就要退步。

Either you study hard or work hard, or you allow yourself to lag behind.