what's Done is Done 无可挽回的；过去了就过去了；木已成舟

【例句】
What's done is done. It's time to move on.
过去的已经过去了，现在是向前看的时候了。

What's done is done. no matter how hard you wish or how much you think about it.
木已成舟，不论你多渴望，想再多也没用了。