Use inner conflict to evoke reader empathy.

Inner conflict is essential for two reasons. First, without it you have melodrama. Second, without it your character doesn't evoke the necessary emotional response from the reader.

For example, without inner conflict, you have something like a fairy tale or Godzilla. There's no inner conflict in deciding what to do about Godzilla. Your characters aren't deeply involved, so how can the reader be?

But if your character suffers inner conflict, he evokes reader empathy. Readers strongly identify with characters through empathy. That spell of identification is what securely hooks the reader and induces the Fictive Dream. Without inner conflict, a character in dire straits evokes, at best, pity. Worse, if the character is flawed, like Humbert in Vladimir Nabakov's Lolita, we will loathe him unless you show inner conflict in him.

You can improve a love story, for example, by introducing a cause of inner conflict. What if both are serious about their religion and their religions clash? What if one is a Montague and the other a Capulet?

The stronger the inner conflict, the greater the drama. In fact, with strong inner conflict your story needn't have titanic antagonists, the fate of the free world at stake, or explosive action. A corporate executive may bilk stockholders for billions with less inner conflict than you or I experience in pocketing a quarter of extra change from a cashier. Yet a poor man may agonize over stealing a loaf of bread to feed his children.

Because of his inner conflict, that poor man's story has more potential drama and success than the corporate executive's story does. So, even in a story of pure fun, like the Indiana Jones trilogy, Steven Spielberg gives us moments of great inner conflict that involve us in the important decisions Indy makes.