“Sit, Sequence. Sit. Good dog.” Woof!
Okay, so sequences might not be our favorite four-legged friends, but they sure are killer gifts to the screenwriter. Small and self-contained, a sequence can be kept in mind all at one time, written in one burst of energy, and shaped independent of the others. And there is always more than one way to mix the dough.
Sequences might not be in chronological order, two separate sequences might be in parallel action, or the first act of the story might be delivered during a second act flashback. This is why each story is a prototype, and should be invented anew each time.
But don’t be fooled into thinking that your story can only be unique if you mix the sequences into a bizarre order. Most of the best stories are also the simplest, the ones which find their greatness not in structure or plot but in the uniqueness of their characters.