Last post didn't post...not going to repeat everything.
You CAN do it. Have faith in yourself and CONCENTRATE. Pay attention to your splits (times at each mark), and at the end of the race ask yourself where you could have done better.
You WILL NOT waltz through these. Be prepared to suffer a lot, I mean learn a lot, as you repeat over, and over, and over...
But you will be successful, if you persist. Simple as that.
Watching the explanation/video of the run/course helps a great deal. Do it and notice the split times. But keep at it.