A friend at work this morning honestly asked if success was the only criterion for giving good advice.
"Absolutely not!" I exclaimed. "Failure is just as necessary as success. Without failure there can be no learning. Without failure there is no impetuous to improve."
Failure is a big blinking arrow of places you can improve.
Also, I'm not 100% sure humans are capable of original thought, and the only way new things are invented/discovered, is we fail at doing something, and the result of that failure is the new invention. So the more you can fail, the more chances you have have discovering something new.