I've written on the subject of defeats before but I came across a quote by Maya Angelou that I love:
"You may encounter many defeats, but you must not be defeated. In fact, it may be necessary to encounter the defeats, so you can know who you are, what you can rise from, how you can still come out of it."
We've all suffered defeats. You didn't get the promotion or raise you felt like you had earned. You didn't get the job for which you were SO right. You asked someone out and they turned you down. Failure is a fact of life. I don't know of ANYONE who hasn't had at least one or two failures along the way.
A study by Claudia Mueller and Carol Dweck, researchers at Columbia University, found that it's MUCH better to praise a child for his or her EFFORT instead of their RESULTS. They studied 412 fifth graders, ages 10 - 12, and found that when you praised children for being smart, they began to focus solely on results and began to resist trying anything new at which they might fail. When the children were allowed to choose tasks, those that were told they were smart, tended to choose assignments on which they knew they would do well. Those children that were praised for their efforts at tasks tended to choose tasks from which they thought they might learn something. (You can read the NY Times article here.)
As you're working on becoming a better leader, remember that a failure here and there won't kill you OR your chances of being a good leader. Personally, I'd MUCH rather have a leader that's experienced a few failures in life that someone that's had non-stop successes. I know how the former leader will react when/if something goes wrong. The latter? Who knows?
One saying I picked up over the years is that FAIL is an acronym that stands for First Attempt In Learning.
Get out there and FAIL!