Last night before bed, I happened to be reading Robert McKee's Story and turned to the nature of conflict. It resonated with me.
In it he points out that a choice between good and evil is not really a choice and does not create sustainable interesting conflict. The audience will know which choice the protagonist will make and the story become predictable. True conflict comes when it is a choice between two goods that the protagonist wants or the lesser of two evils. So it is not a straight +/-
Equally, vacillating between two polar opposites becomes tiresome. Basically because the audience feels that all they have to do is wait a bit and it will be reversed.
Choices need to be irrevocable. Once an action is taken, the opportunity has gone. And will not return without a lot of heart ache and hard work, if the protagonist made the wrong choice to begin with.
So conflict happens when the protagonist is forced to make a choice. Protagonists have to be put under pressure. It is about more than simply yearning for something. When the black moment happens, the world must have changed so much that giving up and going back to the old life is not an option. You sometimes need to ask -- what are the consequences and why would my hero or heroine react in this manner? What are they giving up and what are they achieving? What do they think they will achieve and why is that different?
With writing, it is also about going back and polishing craft. You think you know something and then you discover in fact you have fallen back into old patterns as it is easier. And I do need consistently to think about the nature of conflict.