“一旦你下定决心就不会改变主意”用英语翻译

Once you are determined (to do something), you will not change your mind.Once you have made up your mind, you will not change your mind. (该译文有两个mind，不是太好，但可能该句里都是你学过的词汇。）以上供参考。

人工翻译，请参考：You will never change your mind once you make up your mind.

Once you set your mind to won't change his mind