zhè jiàn shì / yǐ jīng / jué dìng / le / pō shuǐ nán shōu / bié / zài / hòu huǐ / le

这件事已经决定了，泼水难收，别再后悔了。

This matter has already been decided; what's done cannot be undone, so don't regret it anymore.