When that happens to me I have to put it aside for awhile I'll browse the gallery here or look online for inspiration. I can't finish a layout if I am not feeling it. That happened to me with a pirate layout I was doing-I must have started and tore it apart 3 times.T ook me a year to finish it but when I did I absolutely loved it. Still do Good luck!
I make mine go stand in the corner until they can behave themselves.
When I get a page that just won't come together, I tuck it in a folder and take it to a crop with me. Then, I let my fellow scrappers take a look and give me advise. One particular time that stands out is when I had a page that "just needed something." A friend said, "why don't you try a rhinestone here, here and here." Now I'm not a bling girl at all...but I set some rhinestones in, just to be polite...and it was perfect. I NEVER would have thought of that on my own.
Here is the end result: