Prototyping is not an activity reserved for children playing with cardboard. It is fun and serious at the same time, as millions of dollars could be on the line for companies if a product is released before it is ready. Ever wonder why google products are always in beta? They are constantly prototyping their ideas!
The reason we prototype as designers is the get products into the hands of our users quickly. By doing this we can gather feedback and improve our designs. Keep in mind we can prototype experiences, with cardboard, or acting out ideas. Prototyping should be fun, laid back and a tangible experience for everyone involved.
We often hear the term "rapid prototyping" used in design cycles. By rapid prototyping we quickly make our ideas tangible, gather feedback and repeat. Quickly.
As designers, we never go from idea to final product. If we did this in the "real-world", mistakes would be rather costly. Start building in extra time for a couple prototyping cycles to take your making skills to the next level!