It might seem like the ability to fail in a small way is in no way connected to success, but it is. Here's how:
Have you ever been on a diet, slipped up and decided the day was shot, you'd restart tomorrow and then proceeded to eat everything you weren't supposed to that day?
Have you ever fiddled away most of a day doing everything but writing, then decided the day was basically over so no point in sitting down to the keyboard now?
Those are big failures. They take you in the opposition direction of your goal.
Learning to fail small means eating a candy bar for lunch, but then having a healthy dinner anyway.
Learning to fail small means fiddling the day away, but finding a half hour in the evening to sit down and write 100 words.
So next time something doesn't go exactly as planned, ask yourself if you're going to be a big failure or a small one. Personally, I think small failures are big successes.