Failure isn't the problem.
It took me years of obsessing over failure to realize that failure isn't really the problem. With something like running, failure is inevitable. No matter how optimistic I am or how many energy drinks I down, I can't sign up for a race on Sunday and run a 15-minute 5K.
What's not inevitable is failing before I fail. At every race, there's a dialog in my head that goes something like this:
Man, I'm kind of tired this morning. This course is awfully hilly. Did I get enough sleep? I bet I didn't sleep enough. My legs are pretty tired. Wow, I'm breathing hard. I wonder if I'm going to PR. I shouldn't be this tired yet. I hope I don't fail.
Sure enough, once that dialog starts, I'm already on my way to failing.
Let failure happen.
Why do we obsess about failures that haven't happened yet? Planning is human nature, and if you do something risky – like organizing a bank robbery – you should anticipate failure and plan for it. With so much of life, though, planning for failure just sets us up to fail.
When I'm running, my body will tell me when it's had enough. Once that happens, I can stop. Until it happens, worrying about when and if it will happen is useless. It's worse than useless – it's creating a path to failure.
Don't fear your limits, or you'll set them far short of your capabilities. Fail when you fail, and not a moment sooner.