Creativity is often just a matter of trying to figure out what comes next. We try and figure out where the next brush stroke belongs on the canvas or what word goes next in a sentence.
In a sense, we almost cast ourselves as prophets as we work. When our prophecy is wrong, our next steps strike the audience as cheap or shocking. We change the established rules of our creation and take the audience out of its reality. If the next step is solid, the audience relaxes and extends its trust to you.
One way to increase the reliability of your predictions is to look backwards instead of forward. Look at what you have already done and draw your answers from that.
The simplest illustration of this is to think of a mystery novel. If you reveal on the last page that the killer was someone who you hadn't previously introduced to the reader, your book is going to be thrown across the room. Obviously, the whole basis of a mystery novel is to make the killer someone who has always been there, but the audience didn't suspect.
The answer is don't keep making things up. Look to the past to find out what should happen now. Know that new elements introduced late in the game will never hold the same weight for an audience that the initial elements have.
The next time you get stuck while you're working, stop looking forward, turn around and see what has already happened. Don't make up something new, use what you already have. It may seem less creative, but it's much more satisfying.