EL PASO, Texas — My heart is racing. My mind replays the race over and over again 30 minutes before it begins, with me envisioning how I will perform. A part of me is very confident, telling me I will run well, while the other part doubts my ability to finish the 800-meter run. The gun goes off. Eight competitors bump and push at my side and I gradually move with them through the first lap. One more to go.