Why do people derail?

What stops people from delivering their best performance? Why did Andy Murray collapse at 2-0 up in the third set of the Australian Open?

The answer might lie in what is referred to as derailing. For reasons unknown Murray lost his concentration and went from playing championship winning tennis to runner up. Being able to stay on top of your focus at key points like this is key to delivering your potential.  The more we know about how and why we derail the better chance we have of stopping events from running away from us.

Do you know enough about the way you can derail?