On your off days (if you have one) you can drop about 50% of your carb calories, but maintain the protein. If you are feeling a little fuzzy eat some fruit.
The reason for this is that the brain is Glucose powered. Glucose is stored in the muscles (as glycogen) and in the liver. For some reason fructose (fruit sugar) will preferentially replenish liver glycogen, and its from the liver that the brain gets most of its fuel.
Tom, yes it almost feels like tennis

Just who's serve is it anyway?