I am deeply passionate about the value of failure. Looking at my own experiences as well as learning from others I can honestly say that I learned most when I failed. The experience is richest, the insight deepest — and sure as hell: It hurts.
Build into your DNA not only a tolerance for failure, but also a deep desire to turn each and every experience in which you failed, into a golden opportunity to learn.
Failure will improve you. Successes are nice (and necessary) but too many victories without an intermittent loss can overinflate your ego and make you less likely to listen (and thus learn).