I once complained that I had ruined every photo before I even took it by accidentally leaving the camera in low-quality JPEG mode (instead of raw mode, which gives much latitude in recovering from exposure mistakes).
Today I did myself one better.
After driving 2½ hours last night to a hotel near a particular spot where I wanted to make a sunrise photo with the family, we got up at 5:15 and by 6am we had parked and were ready for the 30-minute hike to the location, when I took my first shot of the day, of a picturesque ridgeline with a dull warm 40-minutes-before-sunrise light beyond.
The photo that popped up on the back of the camera was stunning: the sky that seemed almost black in person was now in the photo a deep rich blue at the ridge with a lovely gradient to black at top. The day was starting off exceptionally well, except....
... except that unfortunately, I always have my cameras set to not show each photo on the back of the camera immediately after capture (because it wastes battery), so the photo suddenly popping up meant only one thing: the camera was in “demo mode” like it would be at the store, because I'd forgotten to put in a memory card. Doh!
The camera and lenses all went back into the car, and we made the hike sans camera. (Fumie and I both had iPhones with full batteries, but both died from lack of battery within 10 minutes after reaching the destination. I speculated at the time that the battery might have been consumed faster because of the cold, but I didn't really believe it because it wasn't that cold... just a touch below freezing... but both batteries suddenly returned to half full when we got them back to the warm car.)
I guess it just wasn't my day for photography.