This is why it’s so hard to quit and so easy to dream.When Rafael Nadal’s tennis career ends, there is absolutely nothing he will experience that compares to battling on an acre of red clay, in front of more than 12,000 Spanish loyalists (and Zinedine Zidane) who are hanging on his every shot. And then comes the moment when, after an hour-and-a-quarter, that crucial first set down to its pivotal moment, he sees the ball coming to his backhand side with just enough float. He knows he can do the thing he has always done. He can take those few quick stutter steps and shift his hips and hunt that forehand that will seal this first-set tiebreak, on his fifth chance to get the lead he so desperately wants. And he knows, as soon as he takes that inside-out rip, that it is done. He knows that ball is not coming back. Then he’s down in a crouch, punching at the air below his knees three, four, five times. The screams of the crowd are rattling the metal roof of the Caja Magica, basically his country’s national stadium. It’s on and he can feel it: the rush of competition that he and those 12,000 want to feel just one more time, and then one more, and one more, because they know that when it’s gone, it’s never coming back.