I plan five off days after every three weeks. Often, I max the sixth day and discover that those five days were as valuable as training. I learned about this years ago from a Soviet thrower who argued that the single biggest problem with American throwers was chronic overtraining. Bondurchuk had an interesting training idea of going 100% one week, 80% in both volume and intensity and "15%" the third week...active rest of volleyball, swimming and fun stuff. It was called "load leaping," and the idea was to keep trying to pop up on the week after the 15% training with bigger P.R.s.
There is a book called "Consistent Winning" that talks about what you are trying to do with long term, no stop training. The author argues for several total rest days in the middle of severe training.
Recently, I went down to Las Vegas to compete against two of my good friends, Mike and Mindy. They have been training double sessions since June to prep up for a run at 2004 (Olympics). They have really improved their technique and ability to handle a load, but when the ring judge called their name, you could see that the long haul had eroded their ability to "snap." Whether the muscles had lost their stretch reflex or their nervous system just couldn't rewire a big throw, both struggled with nailing a big mark.
So, if you are in a sport that demands high performance, you need to take time off in some kind of intelligent plan to relax and reload. You could probably just keep putting in workouts, but you seem to have found the problem with that already.
If you do the WOD here, truly do the rest day as a rest day. Of course, if you are overtrained (high morning pulse, flu-like feelings, lethargy, generally ****ed off, trouble relaxing and sleeping, difficulty concentration), you may need more than a day or two. The Soviets used to take two months (!!!) of active rest before starting a new year. Today, many O lifters will take a full year off of training (that is serious) before starting a three year push towards the Olympics.
It usually all gets back to your goals. As a thrower, I have some built in things (the season, for example) that allows me to float my training up and down. Maybe you could find a natural way to do this in your training.