It's interesting how concepts pop up at similar times in a lot of places... and the benefit of failure is one that I've seen come up again and again over the last several months.
Failure is a good thing! Sounds kind of oxymoronic, huh? How can failure be a good thing?
We learn from failure -- not success. Successes can reinforce, they can build confidence... but we don't learn from success. After all, to succeed, we have to already be capable of the skill or concept. To learn it -- we have to fail. Failure occurs when we move beyond our comfort, beyond the easy... when we do something that we can't do -- YET.
If you're trying to get stronger -- you have to move weights (body or iron, doesn't matter) that you can't move easily, and that means you must sometimes fail. Maybe it's doing another push-up than you did yesterday, another rep on the bench press, or 5 more pounds in your squat. Maybe it's running that mile a little faster, doing another 10 punches... You have to move out of that comfort zone, or there's no growth.
One of our more regular exercises in class is punching x-ray paper; it's an exercise to assess the correctness of the punch, and probably a worthy topic on it's own. We allow students several practice attempts, then the "final round" is sort of pass/fail: do a bad punch, and you do some push-ups. That fear of failure is a pressure, and we have to put artificial pressures on people so that they can handle real pressures. Lots of students find a punch they can do well... and they coast. That's their "go to" for the exercise. But, every once in a while, a student decides to develop a different punch. That means that they're going to drop for some push-ups as they practice and develop it... because they will fail some. In time, though, they'll perfect that punch... if they accept the failures.
So... go out, try new things... and be willing to fail.