Dont Judge A Book By Its Content

In the movie or sometimes other people say that " Dont judge a book by its cover" it means that dont judge a person by your first impression.

But in my life it seem like it only happen sometimes. most of the time i can say that they judge a book by its content. Most of the time my parents will judge me by how i act without knowing my real intention/meaning..This is  just like a person who do not know who are you, only they can judge that way..It is just like reading a story book, you can imagine how the story is and how the person act but you dont know why they act that way and you judge the book by how it act and not knowing their meaning

So " Dont judge a book content"..