There's Motivation, But There's Also Perseverance
Take a look around. Notice how people are motivated be it positively or negatively motivated. Money, fear and hunger can motivate people. But what about when people are worn down? Not just "winded," but insanely tired.
Most break down to a degree. Some flat out quit. But the elite are able to fight through fatigue. You have whatever motivational factors you have, but when the going is tough, we tend to forget about the motivation and begin to wear down.
I have vivid memories of my dad talking to me about my life when I was a teen. He didn't speak well, nor was he the smartest, but he was consistent and pushed me. He told me often, "always remember to keep strength, leverage and 'stiminuh.'" Yeah he said, "stiminuh" when he always meant "stamina." It didn't make sense to me until roughly 11th grade when I realized I wasn't a "typical" ball player.
I had to remember when I was tired, to fight through fatigue because there's a strong chance my opponent wouldn't be able to fight like I could. (especially in the 400m hurdles) I had to be the "last man standing." That later equated to day-to-day life. Fight through the fatigue of your body if you have to. Fight through the mental fatigue if you have to. It's NOT easy, but it's rewarding when you do.
Ok that's the end of my rambling. Go forth, prosper and dominate.