Watch what you eat prior to the run. I do my pasta no later than 6 pm for the next morning’s run and avoid spicy things or food that upsets my stomach…definitely no alcohol, caffeine, or excessive sugars. On race morning I use the bathroom twice before I go, then take 1 or 2 imodium tablets about 60 - 90 minutes before I run. I also try to avoid drinking excessive fluids and dairy is a big no-no.
Post run, use the bathroom normally and then take another imodium tablet to settle your stomach. Be aware of what you eat and drink and note how it affects you as Gatorade is well tolerated by me but chocolate milk not so much.
Lastly, nerves are a huge issue. One of the best ways is to arrive on time or a little late so you rush to the corral and then run…the thought process being that the less time you have to sit around thinking, the less nervous energy you have deal with.
Helpful Hint: Chapstick - use it across your eyebrows around the curve or your eyes. This will cause sweat to draw to the side of your face and keep it out of your eyes…no need for headbands. Best to use unflavored chapstick