“你不必苦恼”可以用英语表达为"you don't have to worry"或"you don't need to worry"。这个短语的来源源于英语中某些动词后面常常接"to + 动词原形"的语法结构，例如"have to"表示"必须"。因此"you don't have to worry"就表示"你不必担心"。
下面是一些例句：
You don't have to worry about me. 我不必让你担心。
You don't need to worry about the cost. 你不必担心花费。
I'll take care of it, you don't have to worry. 我会处理的，你不必担心。
Everything is going to be alright, you don't need to worry. 一切都会好起来的，你不必担心。