Only if their fears are challenged will they find the strength to overcome them. The most successful authors are those that can pack a story with emotion. I'll watch it over and over. It all kind of mushrooms. Some authors can sit down and create a story as they write.
Motivations have to make sense and seem viscerally real.
Oh, and it has to be exciting. If I find it boring, forget it. Other times I use the outlining feature in Word. I decide on scenes that will advance the story. I note motivations, key conflicts, things that will advance the sexual tension, revelations that enable the hero and heroine to discover more about each other, spots where the villain creates havoc, etc.