There's a path that new ideas tend to follow: ridiculous > radical > generally accepted.
If you are trying to make an exponential jump, or maybe the next big thing, you have to be willing to enter the realm of the absurd. It's here, in this conceptual space, that odd connections or unexpected ideas can form when connections are made between two or more unrelated things.
Forgetting what you know and suspending rational thought is the tough part because it can inhibit the flow of fresh thoughts. You can also talk yourself out of exploring concepts that seem strange or irrelevant.
When you start the creative process with nothing but acceptable ideas, all you tend to end up with is more of the same.