Should I Be Nervous?

Here I sit just 3 days from my first half marathon and I wonder if I should be nervous?  I know that I have worked hard during my training.  I have completed a 12 mile run.  I feel confident that I can finish the distance.  Recently I have had some of my fastest runs, and I feel confident that I can achieve my goal time (Again, you're going down Ohno!). And I honestly question if I am not a little too cocky.

My allergies have been horrendous with the start of the harvest season, but I have been taking Allegra and it seems to have worked with none of the side effects of other drugs.  My asthma has started bugging me along with my allergies, but I have taken a few puffs of my inhaler and I seem to feel fine.  My back still gets a little tired and stiff in the evenings, but I feel markedly better thanks to Dr. Jackson.  But shouldn't these concerns be bothering me a little bit more?

I guess I am ready.  We will just have to see how it all turns out.