OK, that was an attention-grabbing headline. You really shouldn't be afraid. But if you are nervous or excited or anxious or any of those other emotions before the start of your race (regardless of the distance) that is a very good thing.
Salt Lake City Marathon, I was doing my usual routine of book signing and answering 18 quazillion questions. I can almost immediately identify many of the first time runners. They more or less are biting their bottom lip off. Whether they are freaking out about what it is they are about to try, are anxious to just get the race started or a combination of all of those things, I can always tell they just want to get rid of the nervous feeling. I say do not even try.
I have found that the biggest part of being nervous about an event like this has to do with being nervous. By that I mean, it is the nervous feeling itself that is making the runners wig out a touch, not the actual event. I try to tell them that I have run 138 marathons and at the starting line of every one, I have felt butterflies. Heck, if I go more than two months without a marathon, I am a virtual wreck when I toe the line. In May, when I go to cross off New Jersey from the states-I-need-To-run-in list at the New Jersey Marathon, it will have been nearly half a year since I have done a marathon. That is one of the longest pauses for me in my entire marathon career, if not the longest. It will also be on the heels of having just completed the hardest running event I have undertaken - the Pacific Coast 350. I am going to be an absolute mess.
What you do need to do is be aware you have that nervous feeling for a reason. For a first-timer, you have never run that far in your life. For a seasoned veteran, you know what it takes to get to the finish line and are aware it takes pain and sacrifice. For everyone in between, there is the knowledge that this could be a day when you set a personal best or it could be a day of horrific flopping. But until you start running, you are unsure what, if any, of these things it will be.
So embrace the nervousness. Know what it is, however, and refuse to let it take over your mind. Know it is there to keep you alert, on the edge and hopefully painfully aware that you shouldn't be stupid things right now like eating spicy Thai food you have never had before in your life 8 hours before you get up to run. Or you might be getting up for the runs.