The way to build a great anything — a product, a company, a book, a blog, an app, a service, a movie, anything — is not to obsess over not making mistakes. That leads to paralysis. Try to avoid mistakes, sure. But recognize that you’ll inevitably make some, and create a culture and work ethic where mistakes get identified and fixed.
Re-examine all you have been told. Dismiss what insults your soul.
When people are confronted with evidence that is “inconsistent with their beliefs” (ie. the odds of winning by switching doors being ⅔, instead of ½), they first respond by refuting the information, then band together with like-minded dissenters and champion their own hard-set opinion.