Ok, deep breath in...hold for 5, breathe out...repeat 5 times then drink one large margarita (or just go straight for tequila shot!)

I look at tiredness as a good sign, that you are training yourself well, but you will definately need a break soon. My DW definately knows when I am training hard (Poor wife) . Your body will adapt though, as long as you don't push yourself too much harder. By race day you'll feel super human and surprise yourself w/ how well you'll run. I've found a good tool to help determine overtraining is to take your resting pulse every morning right as you wake up but before getting out of bed. I use rest/easy weeks as a base line for what true resting heart rate is. Then I notice that on hard weeks my resting HR can be as much as 6 or 7 beats higher. It also fluctuates on a daily basis, high the day after a hard workout lower the day after an easy one. When my rHR is up about 10% or more from base line, I run slower. If its more than 15% higher, I take a day off.