One of these days I'll be here. John August has some sage words of advice on his blog for those times when an author faces the n+1th revision of their long form story, be it screenplay or novel, and is going insane.
The most obvious is to use better words. The most challenging is to remove a seemingly important scene and make the rest of the story work.
But my favorite is to imagine a secondary plot we're not seeing. This appeals to me because it's something I'm trying to do anyway in order to make my plots more realistic. It goes along with another tip I've read and will have to locate an attribution for: every character is the hero of their own story. It's important to remember that everyone in a story is trying to accomplish something. And John's advice is to figure out what they're doing when they're off-screen/offstage/off-page.