When I was in high school, I was an active member of my schools student council. Now, like most student councils, we were in charge of organizing a lot of events: dances, pre-game parties, pep rallies, prom, senior banquet, state convention- you name it. As a council of 35 like-minded students, it was often difficult to arrange events that were unique from what had been done in the past. We faced this problem a lot. When it came to themes, we had 3 or 4 'cornerstone' themes that we almost always used; when it came to decorations, we had a closet full of decorations we used every year; and when it came to games, well, you can guess that it all got pretty old after a while.
Our biggest issue wasn't that we had such huge undertakings, but it was that we simply could not think of any new ideas, and because of it, school spirit suffered. I wish I could say that we got out of our funk of having too familiar of mental sets, but unfortunately, and apparently, we hadn't been studying up on our psychology.
However, it's important to note that despite how much hard work goes into large events, they can still fail regardless of the efforts of those involved. So for all of you who can think back to high school, and how boring some of your pep rallies were, remember: it's hard to please everyone and always keep ideas flowing!
Despite this, and now that we've all read up on our psychology, the best way to counter a mental set is to just take a step back and take a break. You'll find that when you return to whatever you're working on, you'll be able to think a lot clearer!