This is the most dangerous pitfall of prototyping.
If you are convinced you already have an answer and you are building a prototype to demonstrate that it is right at all costs, you're missing a great opportunity. It is crucial to remain open-minded. It is very likely that you'd be building a prototype based on a hypothesis to make something new and better.
Everyone would love to hear how brilliant the solution provided by their prototypes is, and it's great when it happens. If it doesn't, the biggest mistake you can make is to be protective of your work and fail to see how a negative response is as useful as a good one. A prototype that shows how something does not work is a success as much as one that has been proven ...
