http://www.openculture.com/2016/01/john-cleese-on-the-importance-of-making-and-embracing-mistakes.html

Cleese means to validate only “those mistakes which, at the time they were committed, did have a chance.” A reasonably good try, in other words. There are some absolutes in the world, after all, and there are “true copper bottomed mistakes, like spelling the word ‘rabbit with three m’s or … starting a land war in Asia.”