【If there are celebrities that you are条件状语】, it is best to remember 【that their lives are very different from most people's lives宾语从句】 and 【that though may seem glamorous, they have their own imperfections like everyone else并列宾语从句,其中的though may seem glamorous为插入语,做让步状语】.
句子的主要干是:
it is best to remember 【that their lives are very different from most people's lives】 and 【that they have their own imperfections like everyone else】. 两个that引导两个并列宾语从句.