A while back I was having trouble with the Deadlift. I thought I was performing proper technique, but once the weight began to reach high intensities I suffered a series of back strains. The strains originated from an old injury I suffered right after college and I would have to restart weight-wise on the lift. Through these setbacks I realized that I wasn't keeping my erectors fully contracted during the heavy pulls, putting more stress on the trouble area than it was able to tolerate. This painful reminder directed my focus on keeping my chest up (to tighten the erectors) and squeezing my abs to improve my anterior support on the lift. Luckily the focus has paid off. I've been able to train the lift for over a year without re-injury and have set many personal records since.
This is an example, albeit small in scale, of how failure has helped me to improve. The strains I suffered were not serious, but as anyone suffering from back pain knows, it is a pain you feel constantly. The memories I have of the few days after an aggravation still act as a reminder to keep good position in the lift today. As much as I would have preferred skipping the pain in those instances, I would not be as skilled in the lift without those experiences.
It seems that failure in our society is viewed as something to avoid at all costs. Perfection is celebrated, but unrealistic. When failure inevitably occurs, a lot of us take it as a personal assault on our character. People naturally stop doing things they fail at to avoid these negative feelings associated with the activity. However, for those that persevere, failure can lead to significant growth. If you can accept that failure will happen (constantly) you can reap the benefits that it provides you by learning from each mistake. It's easier to know how to do something right when you know some of the ways to do it wrong.
Of course, it is easy for me to preach perseverance through failure. We naturally do more of the things that make us feel good and avoid the things that make us feel bad. I've certainly quit many things that I did not succeed at right away. What I have concluded (so far) in my journey and improvement through fitness is that there is a key component that allows someone to push through failure to achieve success, and that is passion. I enjoy lifting weights, and therefore can accept failure and missteps in the quest for success. If I didn't enjoy deadlifting, I may have cut it out of my life after my first instance of injury.
When it comes to fitness, find something you are passionate about. In my opinion, that is the most important thing you can do to become successful. Once you have done that, expect and embrace the failures that come along in your pursuit. Your acceptance of failure will lead to learning from mistakes, which will accelerate your path to success.
If you don't fail, you haven't pushed far enough to learn....or to truly succeed.