翻译：一言为定，不许再反悔了。

That's a deal. Don't go back on your words.

两种地道的英式说法
My word is my bond. 字面意思是我的话是我的束缚，差不多等同于中文的驷马难追。
还有一种
What I said is where I stay. 意思是差不多的
希望能够帮到你！

It's a deal !Don't be regreted!
或者是That's sattled!Don't be regreted!

deal ,no turning back

Deal! Don't be regreted!

deal