There's a reason you hear Sprint Cup drivers referred to as the "best in the world"; in many cases, they are; or, at least, the most driven.
They are, to their sport, the equivalent of NFL players or NBA players. There are lots of folks who play the games, but only a select few ever get to be called "elite".
Drivers who get to the Sprint Cup series have been winners most of their lives. Winners catch team owner's and sponsor's eyes; not the guys who run in the middle of the pack. In many cases, the driver won a lot; not necessarily because he was the most talented; but the most determined and driven.
When you're used to winning, not winning is tough. If that goes on for a long time, often, drivers begin to accept defeat, begin to question their abilities and lose their drive.
That's why it was so cool watching Martin Truex, Jr. celebrate in Victory Lane at Sonoma. There were times he doubted he'd ever pick up another checkered flag; but, he never lost his drive. The emotion was real. That's what six years of near-misses and doubts looks like.