Lots of people probably know this, but sometimes you should think inside the box rather than thinking outside the box. A brief article explains this concept.
The problem with just thinking outside the box is that there are too many possibilities and people generally find that overwhelming. What you should do instead is to find a different box and think there. Physicists do this all the time. They get out of their lab and go hiking and suddenly come up with a brilliant idea.
So get out of your room/office or wherever you are and try some different boxes.