Most of the time we don't want to be overt with our descriptions of the inner world of our characters. Character flaws are always better when they are demonstrated a few times before we name them, or discuss them in dialog. We don't want to stop the story, for example, to point out:
"Bob was tormented by nightmares, caused by sleep apnea, both of which keep sleep from being rejuvenating. His denial of the importance of either condition causes him to suffer from memory lapses, lack of attention and depression."
Using dialog to get this information out to the reader is one method. Using dialog to hint at the issues and then show other events, which lead to Bob's sleep apnea problem is a stronger solution. The use of subtext, by demonstrating the results of his condition, in combination with the other two at various levels is far more powerful.
When an idea or new material or social aspect of a story is important for the reader to take note of, we want to make sure the reader has a chance to grasp our clues. If we are using non-direct methods and subtext to get the idea across to the reader, we want to adhere to the rule of three.
The rule of three states that we should expose readers to an idea three times.
1. If we mention something once, it can seem out of character.
2. If we mention something twice, readers might suspect it’s important but not pick up on the pattern.
3. If we mention something three times, readers will know it’s important and recognize the pattern for what it means for the character or story.