You have to do the training, you have to put in the hours and do the work. As well as preparing your body, and building up physically fitness. You have to prepare your mind.
Train your brain! Visualise yourself crossing the finish line! Visualise your success!!
Have belief and confidence in you and what you can and will achieve.
Believe you can do this and you will.
Have faith, and when you stand on that start line, be ready to give it your all. Your body can achieve so much, your mind is the one you need to convince.
Just go for it and have fun, enjoy all of it, enjoy the training, enjoy the preparation, enjoy the race and enjoy that feeling of satisfaction when you achieve your goal!!!