The lesson is not that you should make your personal life an open book, but rather, when given the option to offer up details about yourself or studiously stash them away, you should just be honest.

句子主干：The lesson is + 表语从句。

修饰成分：表语从句一：not that you should make your personal life an open book;表语从句二：but rather, you should just be honest;状语从句：when given the option to offer up details about yourself or studiously stash them away。

翻译：其中道理并不是说你应该将个人生活袒露无遗，而是说，面对“坦承个人细节”，还是“刻意将其隐瞒”的选择知识，你应该做的恰恰是诚实。