Here's a fantastic page of them: http://www.quotelady.com/subjects/perfectionism.html
Some good ones:
A child becomes an adult when he realises that he has a right not only to be right but also to be wrong.--Thomas Szasz
Freedom is not worth having if it does not connote freedom to err. It passes my comprehension how human beings, be they ever so experienced and able, can delight in depriving other human beings of that precious right.--Gandhi, 1931
In order to go on living one must try to escape the death involved in perfectionism.--Hannah Arendt
The way to succeed is to double your error rate.--Thomas J. Watson.
I need to read that Arendt book.