Why Athletes Need to Rest

I know a lot of people who train too hard. That might sound funny coming from me but hear me out. I do train hard but I understand the importance of rest.
I want to start with some of the warning signs of over training.

You can't sleep
Your times are getting slower
You are often tired
You have muscle and joint pain when you are not exercising
You have an elevated resting heart rate
And you are often in a bad mood

So just what is happening to your body during over training to make you feel this way? Its not what is happening but what's not happening. Your body's repair and maintenance functions aren't working well and in extreme cases aren't working at all. During rest ( rest = Heart Rate at 50% or less of Max) you repair tissue, replenish glycogen and build muscle.
If you don't get enough rest the relatively minor tissue damage of normal training doesn't get fixed and you will constantly feel sore and possibly cause serious harm. If you don't rest your body will use up all glycogen stores and not be able to top them off resulting in fatigue and poor performance. And if you don't rest all that hard work will not result in any strength gain because, as you should have learned in P.E., muscles don't get stronger when you are working them but only during the rest periods between workouts.

Right now I go three weeks on and one easy week but the weekly (on) schedule is one day completely off. Two easy days were I mostly focus on technique. Two medium days and two all out days. Rest is an important part of an athletes life.