As a writer, it is essential to create characters as complex as real-life people, with likes, dislikes, friends and enemies, joys and worries, with a past and a future (unless you plan to kill them). A good writer will know her characters as intimately as she knows herself, her best friend, her husband, or children.
As a normal person, I wondered how many people, including writers, actually, truly know themselves? Or, better yet, if you were to hand out questionnaires to your friends and family members to describe you, how closely would their answers match your own? Do you see yourself the way others see you?
I have written two novels that my beta-readers describe as "definitely publishable", and yet, I can't hook an agent. It has been said that query letters are often so difficult because the writer is too close to his or her own work and therefore can't talk about it objectively, especially in 250 words or less. I must be one of them. I guess I need to get better at self-promotion and sales!
There are myriad examples of people who behave one way in public and the complete opposite in private. Any man or woman who's had an affair, is an easy example, but also actors who pretend to be happily married and then suddenly announce they're getting a divorce. Politicians and back-stabbing friends would be good examples. Two-year olds who've learned how to lie and bulimics also qualify.
But I contend that some innocent, well-meaning people often have no idea how they come across to others. Ego is often involved: some people have too much, others have too little. Still others just WANT to be someone they're not, so they act like they think they're supposed to, but not in ways that are true to themselves (stiletto shoes, plastic surgery, dyed-blonde hair, a car he/she can't afford?).
Interesting... this could go on and on. Sounds like a great conversation to have over a glass of wine.