We certainly learn more from our failures than from our successes. When we are successful in something we arranged before, our brains develop endorphines which are responsible for our happines. However, we often don't realize that and just keep going on. When we face a failure, we need to stop and give it a while to think of what caused such a proceeding. And that's a moment we often find out the answer and get much more ready for the second attempt.
