How much fight does Rafa have left in him?

How will we explain Rafael Nadal to kids 25 years from now? What will we say? That he "fighted" a lot? That he gave everything every damn time? But isn't that sport? Isn't that what everyone does?

But how will we explain that Nadal's fight wasn't like anyone else's fight? It was spelt the same but didn't feel the same. Climbers on Everest will tell you about the Death Zone, above 8,000m, when the body starts shutting down and judgment starts becoming impaired. It must be the tennis equivalent of playing Nadal over a long match. It's all too much.