You can't go back and change things that have already happened.

你不能回过头去改变已经发生的事情。

youdao

You can always go back and change things if you make a wrong decision (until the specification is formally approved, of course.)

如果做了错误的决定那么总是可以回过头去做更改（当然是在规范正式批准以前）。

youdao

Once a relationship ends, you can't go back and change things no matter how much you want to, so it's best to stop beating yourself up about the past.

当一段关系结束，无论你有多想，你都回不去了，也改变不了任何事，所以关于过去，最好就是停止自责。

youdao