Definition
A phrase indicating that since one has started or become involved in something, they should complete it, even if it has become more difficult or complicated than initially anticipated.
一做不停，要做就做到底。
I only intended to help a little with the project, but now that I've started, I'm in for a penny, in for a pound, and I'm going to finish it.
我本来只打算稍微帮忙这个项目，但既然已经开始了，我就一不做二不休，要把它完成。
We've already spent a lot on renovating the house; now that we’ve gone this far, we might as well be in for a penny, in for a pound and complete the entire renovation.
我们已经花了很多钱装修房子；既然已经走到这一步，不如一不做二不休，把整个装修完成。
He originally just wanted to try making a video, but now he’s decided to be in for a penny, in for a pound, and do his absolute best.
他原本只是想试着拍个视频，但现在他决定一不做二不休，全力以赴。