on Writers Helping Writers:

Being able to write realistic, consistent, multi-dimensional characters is vital to gaining reader interest. Doing so first requires we know a lot about who our characters are—you know, the obvious stuff: positive and negative traits, behavioral habits, desires, goals, and the like. But it’s not always the obvious parts of characterization that create the most intrigue. What about the things your character is hiding?

Everyone hides. We hide the goals we know are wrong for us, opinions that may turn others against us, or feelings and desires that make us feel vulnerable—basically anything with the potential for rejection or shame.

The same should be true for our characters. When characters are cagey out of a need to protect themselves from emotional harm, readers understand that. It makes the characters more authentic and can pique your readers’ interest as they try to figure out the secret or worry over what will happen when it comes to light.