agree with ukathleticscoach - i would get trounced in workouts by teammates with more raw speed. come race day, i knew that i was in the driver's seat if i found myself on their shoulder with 300m to go.
also, you need to have unwavering confidence and drive / "will to win" over that last few hundred meters. as ukathleticscoach said, when you make your move - go all out.
think about relaxing your muscles as you are kicking ... relax and go.
you have to stay calm and in control until it is time to pull the trigger, then you go like there is no tomorrow.
imagine that you are in the olympic 1500m final, and kick to win.
random thoughts and idioms ... about what you should be thinking.
"take no prisoners"
"this f**ker is not going to beat me"
"lay it all on the line"
"go big or go home"
"pedal to the metal"
"it's showtime!"
you need to rehearse kicking and winning in your head.
you need to rehearse in practice - focus on catching and passing a teammate in practice, pick out a telephone pole, mail box, etc on your training run and sprint to it.
also, if you know that you have given it your best shot and you know that you did everything right, it makes getting out kicked a little easier - keeping in mind that there is always next week, next year.
*this is all assuming that you have the overall fitness and conditioning necessary to get you to the point where you are able to execute your kick effectively. In the words of the great Juma Ikanga "The will to win means nothing without the will to prepare."