Quitting the dream

I am trying to patient with the fact that my son wants to quit swimming. Never mind that he seemed to like it, actually made some friends in the neighborhood, that the zen of it seemed to calm him, that he wanted to emulate Michael Phelps. Swimming is hard. Too hard. Michael Phelps he is not. But I wonder, at what point do you let a kid quit? Do you put up with tears before every practice? Force them to do something they clearly do not want to do? I wonder what Michael's mom did? Surely Michael wanted to quit once in a while. Was she patient, letting him make up his own mind, or did she force him, enduring the tears. I don't think I have the heart to endure tears. I guess I'm gonna let him quit. But it makes me sad. Kind of feels like the death of a dream, something that seems too soon for a 9 year old.