Physiologically, you kill yourself (and your eventual time) when you go out faster than your eventual overall pace. Of course, the problem is that you don't know what your eventual overall pace is going to be until you finish the race. Catch 22? Not really.
Look, coaches have been telling their athletes to run by pace for as long as there have been coaches and paces. And you know what? Athletes rarely hit the correct splits. Why? See the first paragraph: because you can't know what pace you're capable of running that day until you've run it. There are so many factors that play into your eventual time (climate, your personal fatigue, the other racers, other things going on in your life) that you can't predict your "correct" pace.
So try running by how you feel - and run smart. If you're a quarter mile into the race, ask yourself if you really believe you can maintain the pace you're on for the remainder of the race. If the answer is yes, then great. Keep it up. If it's no, then slow down. Just as most runners will constantly check their watch, constantly check in with your body. You know your body. You've learned what increasing fatigue feels like in interval workouts, time trials, and previous races. Trust yourself.
When you race smart, the times eventually come. When you race to please your watch, you live a guessing game - "I guess this is what I can run today" - that will just come back to bite you.
Good luck!
Oh, and even pace for most of the race with a hard last 200-600 meters is the way to go. Running hard early recruits faster-twitch fibers that burn more muscle glycogen and fatigue more quickly - save those until you really need them.