A quotation from the full collection:

Perhaps there was no way for the young to be serious without being tiresome. They lacked that all-important dimension of physics: torque. Too much time ahead, too little behind, like a man trying to carry a horizontal ladder with a grip at one end. Not even an honorable passion could balance very well. And while jiggling hard to just keep your balance, how could anything ever be funny?

—Nancy Kress (in Beggars in Spain)