Last week's suggestion for improving you mental flexibility was pretty straightforward - just continue to expose yourself to new ideas. This week's suggestion is going to be a little further out there.
Next time you read a work of fiction, try an convince yourself that the story is actually true. This is not too difficult if it is a romance or detective fiction. Such things could actually happen and many times are based on true stories. However, what about horror or science fiction? Could you convince yourself that Stephen King's The Stand or Micheal Crichton's The Andromeda Strain really happened? Could you convince yourself that either is based on a true story?
Actually, the premise of The Andromeda Strain (a lethal microbial life form was brought back to earth on a space probe) is plausible. So, is the premise of The Stand (the military experiments with a deadly virus which escapes into the world). Since they are plausible, they could have really happened. Why wouldn't you have heard about them? Well, there are lots of reasons why such events might be covered up. As you look for explanations to support your claim that these things really did occur, you find that it isn't that difficult to come up with plausible scenarios. In fact, this is what conspiracy theorists do all the time.
The point here is not to make you paranoid or to turn you into a conspiracy theorist. The point is to show you that, with the proper motivation, it is not that difficult to convince yourself of something. And, if you managed to convince yourself of something here that you know is not true, how many of the other things that you believe to be true are nothing more than things you have convinced yourself of in the past for various reasons.
For any given person, much of what they believe to be truth is, in fact, not true. George Washington never did cut down a cherry tree. And the people in Columbus's Day did not believe the world was flat. Many of you believed, at some point, that Pluto was one of the nine planets. Similarly, for any given person, some of what they believe to be false, is, in fact, true. Nobody has it all exactly right. But your mind, vulnerable to inflexibility, will lead you to believe that you do have it exactly right. Hopefully, the mental exercise described here will help you maintain greater flexibility and allow you to update your view of the world as new information comes along.