I spent 4 days hiking near Big Sur a couple of years ago. Felt crazy out of shape 1 mile in and could not figure out why. Out of breath, achy...turned out to be the flu but manageable for the two days hiking in. Turned around when the fever crept up, but still had two days hiking to get out. My plan was to get long exposure night shots of the stars, so on night 3, after a day of feeling like crap, I dragged myself 2 miles up to an outlook, set the camera on long exposure and hoped no one would steal my very expensive gear overnight. Dragged ass back to camp and woke the next morning feeling even worse. Hiked back to the outlook to get my gear, looked at the camera, no images at all. Forgot to turn off auto-focus, rendering the camera inoperative at night. Hiked back to my car, got a hotel, slept for two days and then flew back to Boston. FAIL.