In any story, the problem gets worse in the middle for the main character. Or at least it gets more complicated, more difficult, more dangerous, etc.
They are generally not “winning.” They’re overmatched by whatever they’re involved in.
The difficulties of writing the second act of a screenplay — or plotting out the vast central section of any story — lie in achieving that effect.
After all, if your main character is actively focused on solving their one big problem and/or reaching their one big goal in every scene (which they should be), then real progress should be made, right?
Well, yes and no. Forward motion should happen, but with it should come all kinds of other bad stuff, so that the net effect is that things build to a big crisis, usually about 3/4 of the way in. This “All is Lost” moment doesn’t usually come out of the blue. It’s a result of “bad guys” (or problems) “closing in,” prior to that point (to quote Save the Cat).
To achieve this, a writer needs to give their main character powerful oppositional forces (not always a specific antagonist character), which are acting against them, in a “punch-counterpunch” sort of fashion. Each side is fighting back and forth, reacting to the other, adjusting and trying new things, so that the situation continuously evolves.
The “game should change” for the main character, in virtually every scene. The status of their overall problem/goal — and where they’re at in trying to reach it — keeps developing. It doesn’t just stay at one level, in an ongoing stalemate. It builds.
Sometimes writers try to keep things difficult by having the main character try an approach to the problem/goal which fails, and then another approach that fails, and then another that fails. While sometimes this can work in a quick montage sequence to show time passing, most scenes or sequences shouldn’t end with the main character right back where they started from, before the scene or sequence. If they do, it’s called a “stutter step.” And it could easily be cut from the script, and no one would miss it.
The best scenes are crucial, consequential and necessary, because something happens in them that forever changes the game from this point forward, and leads to new actions, new decisions, new circumstances for the characters, unlike what they’ve experienced before.
Even in a good mystery, where the detective is making some progress toward solving the case (the pilot of the original X-Files comes to mind), with each new clue comes new questions and new challenges. And the tension only grows — which, of course, is what you want.
So the stakes need to be high, the degree of difficulty also needs to be high, and the process of trying to solve the problem and/or reach the goal needs to keep leading to new complications, in such a way that the problematic situation builds and builds, to a breaking point.
Only in the final act, after all seemed lost, is there one last chance to confront the situation in a new way. But even that should not go totally smoothly: it should surprise the main character in some ways, throw them off their guard, and force them to improvise.
That’s ultimately what we like watching characters do: fail to get what they want, and run into new difficulties, which they have to react to, and try to figure out a way to address. Then we like to see them put those new plans into motion, and not quite succeed with them, either — but in new ways, that “change the game” from what it was before. If you read Robert McKee’s book Story, he talks about this as the basic anatomy of a scene.
When in doubt, punish the main character more, make it harder and worse, and complicate the situation. Add conflict and problems. You almost can’t have too many of those. But a lot of scripts suffer from having too few — or from having an overall story problem that doesn’t really build enough, isn’t dynamic, and kind of stays too much the same, throughout.
George M. Cohan’s old saying went something like this: “In the first act, you get your main character up a tree. In the second act, you throw rocks at them. In the third act, you get them down.” The nature of those “rocks” is really key. They should get bigger and more dangerous, and the main character should be losing, despite taking actions to try to avoid or combat them. How you keep those “rocks” evolving — as well as their reaction to them, and plan to defeat them — is the foundation of your story.
I also recommend my "Ten Key Principles Successful Writers Understand", and my series of audio downloads. And if you'd like me to read something you're working on, check out my consulting page.