Are you anything like any one of your characters?

I hear from others that it's pathetic to add yourself to a story or to add a part of you to your characterm For example, a girl who wasn't liked in school writes about a much younger girl who had a rough childhood and wasnt liked either by teachers. The girl in the story still has many differences from the writer, but the writer decided to add that part of her life to her character because she's been through it firsthand and it suits the story. What do you think?