Concentration, Music and Endurance Events
Concentration is one of the most underrated attributes of the endurance athlete. The ability to stay psychologically present in what you are doing and not allowing yourself to mentally "drift off" to often is key to getting the best out of yourself on the day. Which is - unless you're just there to finish - what you've been training for.
This shouldn't be interpreted as putting on a mean looking face the entire race and pushing every ounce of life out of your body, as would a sprinter. That would be no fun as well as exhausting. Some lapses to acknowledge a family member in the crowd or to share a joke with a fellow competitor can provide great mental relief during a long event. But distracting yourself from the task at hand for too long or too often, while it may get you across the finish line, may be undermining the performance you're capable of.
I'm sometimes asked what I "think" of while I'm racing. I can generally occupy myself, even in the longer races, doing pace and time calculations in my head, monitoring my sensations and competitors, trying to conserve energy, taking the straightest line on the course and planning when I'm going to drink and eat.
Which brings us to the question of headphones and music. While research has shown it to be beneficial for endurance in untrained individuals it's less conclusive for the more competitive racers. "When exercisers need to devote their full attention...to their physical limits (“listening to the body” in other words) the use of music should be limited." was a take away from a review of the research.
A strong focus can help accomplish mental tasks such as pushing negative thoughts out of your head, correcting your technique or holding the right pace free from the distractions of your competitors. All these things will help you get to that finish line faster.