The ability to continue when training gets difficult is the greatest opportunity to grow as an athlete and a human being. If you can find the right encouragement within you during a tough moment, you're giving yourself a vital tool to accomplish many great things. Sometimes the same verse can get stale, so I think it's important to keep mantras fresh and effective. That being said, the most significant words my coach Terrence Mahon ever told me was as I was heading to the starting line of the Chicago Marathon in 2005. My goal was to win the race, and my training had gone very well. He is a guy of many words and on this day he simply said 'Define yourself.' It was such a powerful statement and I rehearsed it a million times on the streets of Chicago that morning—and got my first marathon win.