I agree with everyone else. When you toe the line, give it a full race effort. That doesn't mean that you have to reduce your workload (subject to the note below) in order to race. It just means that when you step to the line, regardless of what else you have done that week, you respect the ritual of racing so that it remains as a hallowed event in your mind. As another posted out, once you view racing as something you can do at less than a full effort, you have taken the first step down a slippery slope.
My one qualifier is that you obviously need to integrate the races into your training pan. While there was once a time when it was fairly common to do a track session, a tempo session, a race and a long run in one week, the conventional wisdom today is that this is too much work for most people in one week. so you will need to use your race to replace one of your workouts. My rule of thumb is that a 5k replaces a track session, anything longer than a 10k replaces a tempo session, and 10k can go either way. As to 10ks, I would have them replace a track session if race week is supposed to be a less intense week on my calendar and I would have them replace tempo sessions during more intense weeks (I try to cycle through different mileage amounts during my cycles, and I make my high mileage weeks less intense and my lower mileage weeks more intense).
Finally, no matter what you do, never, ever say to your competitors before or after the race "I was just using this as a tempo." Show them the respect that they deserve.