"One thing I learned is that while your vision should never change, you should keep trying different strategies until one works. If you can fine-tune your instinct and have confidence in it, then you can keep taking different bites of the apple and keep approaching the problem in different ways until you get it right."

Source: http://businessweek.com/articles/2012-04-12/how-to-fail-mark-pincus

"I think failing is the best way to keep you grounded, curious, and humble. Success is dangerous because often you don’t understand why you succeeded. You almost always know why you’ve failed. You have a lot of time to think about it."

Same source.