+1 to all of the above. My will to train is much greater than my ability to recover from training. Which sucks. Lots.
All I've done to get round it is ride every other day, take two days off if I get tired and crucially think of my rest day as training – active recovery is a good mindset to get into, as is training hard and resting harder. I use my resting heart rate as a good indicator of being tired too, along with disturbed sleeping patterns. If I get run down or fatigued I know that as I get a slightly sore throat – time to ease down for me then.
Vitamins and supplements help – Cherry Active helps loads for recovery as will protein shakes. I hate to say it but cutting down on the merlot helps lots too. That's the hardest bit for me :-)