On sheep and goldfish
Here's an old story readjusted for the modern world:
A project manager, a developer, and a tester are riding on a train in Scotland. Along the way, they pass a black sheep. The project manager says, "Hey look! The sheep in Scotland are black." The developer scoffs and says, "There is at least one black sheep in Scotland." The tester shakes his head and says, "To the best of my perception, there is at least one sheep in Scotland which is black on the side facing us."
That being said, as a tester, I try to make as few assumptions about what I'm seeing as possible. The trick is to look at every aspect of the product as though I'd never seen it before. This is rather difficult since I've been working on testing Visual Studio's Team Foundation for about a year and a half now. It's pretty amazing how hard it is to pretend to have the memory of a goldfish.
Be that as it may, I devised a clever ruse to force myself out of a routine. I'm right-handed, so use the mouse with my right hand. Today, I switched the mouse over to the left. This helped break my normal patterns enough that I could "learn" the product again.
Note- not recommended for people easily frustrated.