One of my best friends works for NASA and a few years ago he gave me a Mission Control shirt that says "Failure is not an option". That's a fantastic motto if you're working in a situation where a mistake can cost lives, but a terrible motto if you're trying to innovate and invent. I've often half-joked around the office that our motto should be "Failure is an option". If you want to really push yourself, you've got to know that it's OK to fail sometimes. You pick yourself up, brush yourself off, and try again--failing is often the fastest way to learn. We've also been conditioned to think it's the most painful when it isn't--not by a longshot.
Scott Berkun blogged about the following video, which is basically a soft-sell ad about Honda, but at heart it's a story about the importance of failure. Well worth a watch.