It's not just heart.
Some people are just better at their sport of choice. They have an innate ability in their sport that can't be measured by anything other than the results on the field of play. Someone can be bigger, faster and stronger than Emmitt Smith, dedicate their entire life to football, yet never even play in the NFL, much less become a star. Taco Charlton can bust his hump for 15 years, and he might not be as good as Bosa, or any other good passrusher.
There is no yardstick to account for a person's God-given ability.
That's not to say Taco won't become a good player, he might.