Writing is hard and it can be downright painful.  Getting started sometimes can be an issue, getting through the second act can be overwhelming, and just finishing the third act can feel impossible.  Here are some random tips and thoughts for you to consider! 

1. If you are struggling to get your story going, meaning that opening few scenes, skip those and jump to the inciting incident. This event propels your central character into action.  If you don't know what that scene is... you weren't ready to start writing.
2. If you're sitting at page 40 or 50 and are stuck that means your second act has not been properly thought out.  Make sure your central character (protagonist) has a clearly defined need or goal and that you have some kind of theme or internal struggle that he or she is conflicted by. That can help fire up the story.
3. Third act problems usually reside in the first act.  You didn't raise a question that has to be answered in the third act.  The goal or need of the central character was not strong enough to sustain and support the narrative spine.
4. If you're constantly not sure what your next scene is you either do not have the story plotted out well enough or your scenes are not helping to move the story forward. Remember each scene has to accomplish something and push the story forward onto the next scene.
5. If you get to the resolution and have completed the central character's journey but yet feel like you're not sure what the story was truly about (theme) that's ok. Put the script away for a couple weeks don't think about it then come back and reread it.