I agreed this was completely natural, and made the observation that plots are essentially shaped like diamonds. In the first act, you open a door to enter the narrative, only to face an endless variety of choices for character, action, setting, problems, solutions, what have you. These options burgeon before you, the writer, and you must not only choose them, but allow them to multiply like rabbits until you reach the level of complexity which makes the work interesting and sustains the interesting aspects of the story.
The second act is where you (mostly) stop throwing open new doors and begin to concentrate on what all those choices mean to the characters and their story. This is the waist of the diamond. The famous "muddle in the middle" comes from this shift in both momentum and direction, when the author has to figure out what the heck it all means and drive the story in some direction or another.
The third act comes back together, the possibilities of the plot being pruned off one by one, until it narrows to a conclusion balancing between dramatic inevitabily and surprise. Like all good endings, it reflects the beginning — the other tip of the plot diamond.
Thoughts? Corrections? Comments?