Lois Mcmaster Bujold said this quote

They stared at her curiously, and she caught snatches of conversation in two or three languages. It wasn't hard to guess their content, and she smiled a bit primly. Youth, it appeared, was full of illusions as to how much sexual energy two people might have to spare while hiking forty or so kilometers a day, concussed, stunned, diseased, on poor food and little sleep, alternating caring for a wounded man with avoiding becoming dinner for every carnivore within range - and with a coup to plan for the end.