My leg hurts, but I'm still going ice skating today

Everyone has their own theory about the correlation between athletic ability and trading ability, so here is my stab.

There is a natural human inclination to avoid pain and to seek pleasure. Some people are miswired, and they seek pain and avoid pleasure. Neither of these two fundamental psychological constructs correlates with trading success.

However, an athlete has experienced, in a very visceral way, that it is possible to work through pain in order to achieve pleasure. And this is exactly the stamina that separates the squishies from the robos.