Why would Rat count himself lucky if he was in the middle of amputations, sadness, and despair? What is worse?

Rat believed that having to hump and be in the field was the less attreactive option.

It was gory work, Rat said, but predictable. Amputations, mostly—legs and feet. The area was heavily mined, thick with Bouncing Betties and homemade booby traps. For a medic, though, it was ideal duty, and Rat counted himself lucky. There was plenty of cold beer, three hot meals a day, a tin roof over his head. No humping at all. No officers, either.