Most amateur scripts have a good first act and a workable second. They lose the reader in the third — and almost always for the same two reasons.
Mistake 1: the climax is action, not decision
A climax isn’t the loudest scene. It’s the one where the protagonist makes the hardest choice. If your third act has a big fight but the choice was already made in act two, you’ve written a sequence, not a climax.
Fix: name the choice. Write it on an index card. If you can’t find one — your third act is decoration.
Mistake 2: the resolution explains itself
If a character has to say “I’ve changed”, they haven’t. Resolution is behaviour, not statement. The audience watches the change happen — they don’t need it summarized.
Fix: cut every line in your resolution that explains. If the scene still works, the change was real. If it doesn’t, you’ll need to go back to act two and earn it.
How to test your own draft
Read only act three. If it makes sense without acts one and two — you have a problem. The third act is supposed to be impossible to understand alone. It’s a payoff. Payoffs require setup.