On the run

I'm heading out to do 9 or 10 miles. Why do I get nervous before each and every long run? Does everyone else who runs do that? Honestly, I'm writing right now because if I tell you that I'm going to do it, then I've made a promise that I have to keep, which is not a bad strategy. But I just get so scared. Will that ever change? Maybe I'll ponder that as I trot along. Gotta run...