According to the Mayan prophecy the world will end at the stroke of midnight this eve marking the conclusion of the 5,125-year “Long Count” Mayan calendar. However to ease at least one burden as you go to bed tonight let me put your mind at rest about taking rest days from your training regime.
When you are deeply into your running and training and its going well its hard to take a rest day. You believe that a rest day will undo all your good work.
However, the reality is that you only start to loose fitness after 10 to 15 days. Remember how hard it was to get in shape, well it takes time to lose it too. After a period of training, rest lets your body adapt to the work and improve. A day off every seven to 14 days restocks glycogen stores, builds strength, and reduces fatigue. Without recovery, adaptation cannot occur fully. Most injuries come from overuse, a day of cross training/circuits, rest, or easy miles can prevent injury.
In fact the only cataclysmic event likely to happen is an injury as you you push your body to destruction. So to avoid doom and gloom of injury listen to the greatest predictor of the future. Your own body and take a rest day.
It could be your last!
For more information about running and fitness visit http://www.run4fit.com
Darrell Smith
run4fit 
Great advice.Lots of athletes forget or ignore the value and benefits of rest and recovery.