A character in a novel of mine—that most dangerous of creations: a novelist writing a novel—observed that there were three types of actions: purposeful, habitual, and gratuitous. If the writer can show a character involved in a number of all three types of actions, the character will probably seem more real.
This occurred to me when I was trying to analyze why some writers who can present perfectly well-drawn males cannot present a convincing female to save themselves—heroines or villainesses. I noticed with these writers that while their heroes (and villains) happily indulge in all types of actions, if there is a villainess, she is generally all purpose; if there is a heroine, she often does nothing but habitual actions, or nothing but gratuitous ones."
— Samuel R. Delany, “Characters” in “On Writing”. (via thymoss)