I'm sure I wont be the only person with this problem. In races I can be guilty of going off at the wrong pace either too slowly or, more probably, far too fast and then running out of steam half way round.
I did a race at the weekend and changed tactic. For the first half of the race I sat on the shoulder of someone who is a similar pace as me but has more consistent pacing for the first five miles and then kicked on at my own pace once I'd passed half way. It's probably one of the best races I've ran because the pacing at the start was right.
However the pacing was only right because I was copying someone else. How do I learn how to pace myself? When I set off too fast it's not until the damage is done halfway round that I realise I probably went too hard at the start.