The moment you think about giving up,think of the reason why you held on so long. 每当你想放弃的时

The moment you think about giving up引导状语从句，
think of the reason why you held on so long为什么用think？是祈使句么
因为找不到主语

The moment you think about giving up,think of the reason why you held on so long. 每当你想放弃的时候，想一想是什么支撑着你一路坚持。

翻译不用了

The moment you think about giving up，think of the reason why you held on so long.
the moment用来引导时间状语从句，think of the reason why you held on so long是主句，该主句是祈使句，所以没有主语。

应该是 the moment you think about giving up,think of the reason why you held on so long.吧 你一想到放弃，就会想到你已坚持那么久原因

这句话得主干是you think about giving up,(that)think of the reason 。 The moment you think about giving up,think of the reason why you held on so long.这句话省略了that ，“think of the reason why you held on so long.”作为前面的补充说明，要放弃时就要想起“the reason”。而“ the reason” 后接的是对the reason 的修饰。