If you've been hanging around writers circles at any point in the last fifteen or so years, you have probably run into the concepts of "call to action" and "refusal of the call" from the hero's journey. There's another pattern which is something like the flipside of this call/refusal pattern, though, which centers around the concept of what is forbidden to the protagonist.
As a brief reminder, the call/refusal comes in the early part of the structure referred to as the hero's journey, the quest myth, or Campbell's sun god monomyth. This is a powerful and enduring story structure which begins with an extraordinary character, unaware of his true nature, who has been stashed in an ordinary world for safekeeping (or for some other purpose) during his youth. The call to action is the first major step in this character's evolution. An external force intrudes on the ordinary world and makes some request or demand of the protagonist. Whether due to fear, uncertainty, or a general feeling of unreadiness, the hero refuses this request or demand. Ultimately, of course, the hero changes his mind and does it anyway.
Some story analysts have suggested that the refusal of the call -- more specifically, the way that this refusal allows the protagonist to demonstrate humility, uncertainty, insecurity, or other less heroic emotions -- is necessary to allow the reader to bond with the character. Without it, the hero might seem foolhardy or arrogant. With it, he seems more moderate or tempered. So this might be the purpose of this refusal to do something we all know he'll end up doing anyway.
This particular story structure is naturally well-suited to action/adventure, fantasy, some scifi, and can be adapted to other story types. But there are other structural models, and one that I talk about quite a lot is the fairy tale structure which lends itself well to horror and romance. (By the way, if you've ever wondered why paranormal romance works so beautifully as a subgenre, but scifi romance is a trickier marriage, it may have something to do with these structural tendencies.)
In fairy tale structure, we start with a virtuous character in a hostile or treacherous world. (Virtue, by the way, doesn't mean sexual innocence in this context. It means the characteristics which we most value in that type of character.) Frequently, the hostility or treachery in the environment follows the loss of a key family member -- think about what happens to Cinderella when her dad dies.
But there might be another aspect to the hostility or treachery of this world, and it comes in the form of what Vladimir Propp (who analyzed a wad of Russian wonder tales much the same way Campbell analyzed all those sun god stories) calls an interdiction. This just means that someone in a position of authority -- or perhaps, an authoritative entity -- has officially banned some act. There might be legitimate safety reasons for that interdiction. "Don't go into the woods at night." Well, we all know what happens when you ignore this rule and go into the woods at night anyway. Freaky bad stuff.
But hey, we're going into the woods anyway, right? Because that's the next step in the structure. Just as the call to action is met with a refusal, the interdiction must be violated. If Cinderella is banned from going to the ball, you'd better be sure she's going to find a way to get to the ball. The ban must be broken, and the forbidden must be experienced. Yes, there will be problems. But those problems will test the heroic traits in a way that proves them to be true and worthy of reward. So, even though we might think it's bad for a "virtuous" character to break the rules, really, it's all part and parcel of that virtuous nature. (This technique, if not this exact structure, is sometimes used in "rebel cop" stories, too. Anyone want to discuss the difference between using this as a mid-scale character technique and using it as a structural element?)